Piggyback intraocular lens that improves overall vision where there is a local loss of retinal function

ABSTRACT

Systems and methods are provided for improving overall vision in patients suffering from a loss of vision in a portion of the retina (e.g., loss of central vision) by providing a piggyback lens which in combination with the cornea and an existing lens in the patient&#39;s eye redirects and/or focuses light incident on the eye at oblique angles onto a peripheral retinal location. The piggyback lens can include a redirection element (e.g., a prism, a diffractive element, or an optical component with a decentered GRIN profile) configured to direct incident light along a deflected optical axis and to focus an image at a location on the peripheral retina. Optical properties of the piggyback lens can be configured to improve or reduce peripheral errors at the location on the peripheral retina. One or more surfaces of the piggyback lens can be a toric surface, a higher order aspheric surface, an aspheric Zernike surface or a Biconic Zernike surface to reduce optical errors in an image produced at a peripheral retinal location by light incident at oblique angles.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit under 35 U.S.C. §119(e) of U.S.Provisional Application No. 61/950,757, filed on Mar. 10, 2014, titled“INTRAOCULAR LENS THAT IMPROVES OVERALL VISION WHERE THERE IS A LOSS OFCENTRAL VISION.” This application also claims benefit under 35 U.S.C.§119(e) of U.S. Provisional Application No. 61/987,647, filed on May 2,2014. The entire content of each of the above identified applications isincorporated by reference herein in its entirety for all it disclosesand is made part of this specification.

This application is also related to U.S. application Ser. No. ______,filed concurrently herewith on Mar. 10, 2015, titled “INTRAOCULAR LENSTHAT IMPROVES OVERALL VISION WHERE THERE IS A LOCAL LOSS OF RETINALFUNCTION,” Attorney Docket No. AMOLNS.055A4. This application is alsorelated to U.S. application Ser. No. ______, filed concurrently herewithon Mar. 10, 2015, titled “ENHANCED TORIC LENS THAT IMPROVES OVERALLVISION WHERE THERE IS A LOCAL LOSS OF RETINAL FUNCTION,” Attorney DocketNo. AMOLNS.055A2. This application is also related to U.S. applicationSer. No. ______, filed concurrently herewith on Mar. 10, 2015, titled“DUAL-OPTIC INTRAOCULAR LENS THAT IMPROVES OVERALL VISION WHERE THERE ISA LOCAL LOSS OF RETINAL FUNCTION,” Attorney Docket No. AMOLNS.055A1. Theentire content of each of the above identified applications isincorporated by reference herein in its entirety for all it disclosesand is made part of this specification.

BACKGROUND

1. Field

This disclosure generally relates to using an intraocular lens toimprove overall vision where there is a local loss of retinal function(e.g., loss of central vision due to a central scotoma), and moreparticularly to using an intraocular lens to focus light incident atoblique angles on the patient's eye onto a location of the peripheralretina.

2. Description of Related Art

Surgery on the human eye has become commonplace in recent years. Manypatients pursue eye surgery to treat an adverse eye condition, such ascataract, myopia and presbyopia. One eye condition that can be treatedsurgically is age-related macular degeneration (AMD). Other retinaldisorders affect younger patients. Examples of such diseases includeStargardt disease and Best disease. Also, a reverse form of retinitispigmentosa produces an initial degradation of central vision. A patientwith AMD suffers from a loss of vision in the central visual field dueto damage to the retina. Patients with AMD rely on their peripheralvision for accomplishing daily activities. A major cause of AMD isretinal detachment which can occur due to accumulation of cellulardebris between the retina and the vascular layer of the eye (alsoreferred to as “choroid”) or due to growth of blood vessels from thechoroid behind the retina. In one type of AMD, damage to the macula canbe arrested with the use of medicine and/or laser treatment if detectedearly. If the degradation of the retina can be halted a sustained visionbenefit can be obtained with an IOL. For patients with continueddegradation in the retina a vision benefit is provided at least for atime.

SUMMARY

The systems, methods and devices of the disclosure each have severalinnovative aspects, no single one of which is solely responsible for thedesirable attributes disclosed herein.

Ophthalmic devices that magnify images on the retina can be used toimprove vision in patients suffering from AMD. Such ophthalmic devicescan include a high optical power loupe or a telescope. Intraocularlenses (IOLs) that magnify images on the retina can also be implanted toimprove vision in patients suffering from AMD. Such IOLs are based on atelescopic effect and can magnify images between about 1.3 times andabout 2.5 times, which will improve resolution at the cost of a reducedvisual field. However, such IOLs may not provide increased contrastsensitivity.

Various embodiments disclosed herein include ophthalmic devices (suchas, for example, IOLs, contact lenses, etc.) that take intoconsideration the retinal structure and image processing capabilities ofthe peripheral retina to improve vision in patients suffering from AMD.The ophthalmic devices described herein can be lightweight and compact.Various embodiments of the ophthalmic devices described herein can focusincident light in a region around the fovea, such that a patient canmove the eye and choose a direction that provides the best vision. Forpatients with a developed preferred area of the peripheral retina, theembodiments of the ophthalmic devices described herein can focus imageat the preferred area of the peripheral retina as well as correct foroptical errors occurring in the image formed in the area of theperipheral retina due to optical effects such as oblique astigmatism andcoma. In some patients without a developed preferred area of peripheralretina, the improvement in the peripheral vision brought about fromcorrecting the optical errors in the image formed at a location of theperipheral retina can help in development of a preferred area of theperipheral retina.

The embodiments described herein are directed to ophthalmic lenses, suchas an IOL, and a system and method relating to providing ophthalmiclenses that can improve visual acuity and/or contrast sensitivity whenthere is a loss of central vision by focusing incident light onto anarea on the peripheral retina around the fovea or at a region of theperipheral retina where vision is best. Such ophthalmic lenses caninclude spheric/aspheric refractive surfaces, refractive structures suchas prisms and diffractive structures such as gratings to focus incidentlight onto a region of the peripheral retina around the fovea.

One aspect of the subject matter described in this disclosure can beimplemented in an intraocular lens configured to improve vision for eyeshaving no or reduced foveal vision. The intraocular lens comprises afirst zone having an optical axis which intersects the retina of the eyeat a location external to the fovea; and a second zone having an opticalaxis which intersects the retina of the eye at the fovea, wherein thefirst zone has a power that is greater than the second zone.

Another aspect of the subject matter described in this disclosure can beimplemented in a method for improving vision where there is no orreduced foveal vision using an intraocular lens with at least two zones.The method comprises determining a deflected optical axis whichintersects a retina of a user at a preferred retinal locus; modifying afirst zone of the intraocular lens to redirect incident light along thedeflected optical axis; modifying a second zone of the intraocular lensto direct incident light along an undeflected optical axis whichintersects a retina of a user at the fovea; and adjusting a power of thefirst zone to be greater than a power of the second zone.

One aspect of the subject matter described in this disclosure can beimplemented in an intraocular lens configured to improve vision wherethere is a loss of retinal function (e.g., a loss of foveal vision), theintraocular lens comprising: a redirection element configured toredirect incident light along a deflected optical axis which intersectsa retina of a user at a preferred retinal locus. The redirection elementcomprises a surface with a slope profile that is tailored such that, inuse, the intraocular lens: redirects incident light along the deflectedoptical axis; focuses the incident light at the preferred retinal locus;and reduces optical wavefront errors, wherein the slope profile istailored to redirect and focus the incoming rays on the preferredretinal locus. The slope profile can be tailored based at least in parton a solution to an analytical equation that is a function of a distancefrom the IOL vertex to the original focus (l), an index of refraction ofthe IOL (n_(l)), an index of refraction of the aqueous environment(n_(ag)), an angle inside the eye to the preferred retinal locusrelative to a back vertex of the IOL (a_(p)), a radial position of theIOL (x), and/or the posterior radius of curvature of the IOL (r), theanalytical equation given by the following:

${{{slope}(x)} = {- {\cos^{- 1}\left( \frac{{n_{aq}\mspace{11mu} \cos \mspace{11mu} \alpha} - {n_{l}\mspace{11mu} \cos \mspace{11mu} \beta}}{\sqrt{n_{aq}^{2} + n_{l}^{2} - {2n_{aq}n_{l}\mspace{11mu} \sin \mspace{11mu} \alpha \mspace{11mu} \sin \mspace{11mu} \beta} - {2n_{aq}n_{l\;}\cos \mspace{11mu} \alpha \mspace{11mu} \cos \mspace{11mu} \beta}}} \right)}}},$

wherein

${\alpha = {\tan^{- 1}\left( \frac{{l\mspace{11mu} \sin \mspace{11mu} a_{p}} - x}{{l\mspace{11mu} \cos \mspace{11mu} a_{p}} - r - \sqrt{r^{2} - x^{2}}} \right)}},$

and wherein

$\beta = {{\sin^{- 1}\left( {\frac{n_{aq}}{n_{l}}{\sin \left( {{\tan^{- 1}\left( \frac{- x}{l - r - \sqrt{r^{2} - x^{2}}} \right)} + {\sin^{- 1}\left( \frac{x}{r} \right)}} \right)}} \right)}.}$

In some implementations, the slope profile can be tailored based atleast in part on an analytical solution to an equation describing an eyeof a patient. In some implementations, the slope profile can be tailoredbased at least in part on simulations performed using ray tracingtechniques. In some implementations, the slope profile can be determinedanalytically using an equation that incorporates an axial length to thepreferred retinal locus, an angle of the deflected optical axis relativeto an undeflected optical axis, and a radial position of the preferredretinal locus. In various implementations, the slope profile can betailored using an iterative procedure that adjusts a portion of theslope profile to account for a thickness of the redirection element.

The redirection element can comprise a plurality of zones. Each zone canhave a slope profile that is tailored based at least in part on thesolution to an equation (e.g., the analytical equation given above). Invarious implementations, a thickness of the redirection element can beless than or equal to 0.5 mm. In various implementations, a curvature ofa posterior surface of the intraocular lens is configured to provide afocused image at the fovea of the retina of the patient. In variousimplementations, the redirection element can be a separate, additionalsurface on the intraocular lens. In some implementations, theredirection element can be a ring structure. In some implementations,the redirection element can cover a central portion of the intraocularlens. The central portion can have a diameter that is greater than orequal to 1.5 mm and less than or equal to 4.5 mm. In variousimplementations, a posterior surface of the intraocular lens can includethe redirection element, and an anterior surface of the intraocular lenscan include a second redirection element comprising a plurality ofzones, each zone having a slope. In some implementations, a posteriorsurface and/or an anterior surface of the intraocular lens can be toric,aspheric, higher order aspheric, a Zernike surface or some other complexsurface. In various implementations, the posterior surface and/or theanterior surface of the IOL can be configured to reduce astigmatism andcoma in the focused image produced at the preferred retinal locus. Invarious implementations, a portion of the IOL can include theredirection element and another portion of the IOL can be devoid of theredirection element. In such implementations, the portion of the IOLincluding the redirection element can have an optical power that isdifferent from the portion of the IOL that is devoid of the redirectionelement.

Another aspect of the subject matter described in this disclosure can beimplemented in a method for improving vision where there is no orreduced foveal vision using an intraocular lens and a redirectionelement having a tailored slope profile. The method comprising:determining a deflected optical axis which intersects a retina of a userat a preferred retinal locus; calculating a tailored slope profile forthe redirection element, the tailored slope profile comprising aplurality of slope values calculated at a corresponding plurality ofpoints on a surface of the intraocular lens; determining opticalaberrations at the preferred retinal locus based at least in part onredirecting light using the redirection element with the tailored slopeprofile; adjusting the slope profile to account for a thickness of theredirection element; and determining whether a quality of an imageproduced by the redirection element with the adjusted tailored slopeprofile is within a targeted range.

One aspect of the subject matter described in this disclosure can beimplemented in a method of using an intraocular lens to improve opticalquality at a preferred retinal locus, the method comprising: obtainingan axial length along an optical axis from a cornea to a retina;obtaining an axial length along an axis which deviates from the opticalaxis and intersects the retina at the preferred retinal locus. Themethod further comprises determining a corneal power based at least inpart on measurements of topography of the cornea; estimating an axialposition of the intraocular lens wherein the intraocular lens withinitial optical properties at the estimated axial position is configuredto provide a focused image at a fovea. The method further comprisesadjusting the initial optical properties of the intraocular lens toprovide adjusted optical properties, the adjusted optical propertiesbased at least in part on the axial length along the optical axis, theaxial length along the deviated axis to the preferred retinal locus, andthe corneal power, wherein the adjusted optical properties areconfigured to reduce peripheral errors at the preferred retinal locationin relation to the intraocular lens with the initial optical properties.

Another aspect of the subject matter described in this disclosure can beimplemented in an ophthalmic device configured to deflect incident lightaway from the fovea to a desired location of the peripheral retina. Thedevice comprises an optical lens including an anterior optical surfaceconfigured to receive the incident light, a posterior optical surfacethrough which incident light exits the optical lens and an axisintersecting the anterior surface and posterior surface, the opticallens being rotationally symmetric about the axis. The device furthercomprises an optical component disposed adjacent the anterior or theposterior surface of the optical lens, the optical component having asurface with a refractive index profile that is asymmetric about theaxis.

One aspect of the subject matter described in this disclosure can beimplemented in an ophthalmic device comprising an optical lens includingan anterior optical surface configured to receive the incident light, aposterior optical surface through which incident light exits the opticallens and an optical axis intersecting the anterior surface and posteriorsurface. The device further comprises an optical component disposedadjacent the anterior or the posterior surface of the optical lens, theoptical component including a diffractive element, wherein the opticalcomponent is configured to deflect incident light away from the fovea toa desired location of the peripheral retina.

One aspect of the subject matter described in this disclosure can beimplemented in an ophthalmic lens configured to improve vision for apatient's eye. The lens comprises an optic with a first surface and asecond surface opposite the first surface. The optic together with acornea and an existing lens in the patient's eye is configured toimprove image quality of an image produced by light incident on thepatient's eye at an oblique angle with respect to the optical axis andfocused at a peripheral retinal location disposed at a distance from thefovea. The image quality is improved by reducing oblique astigmatism atthe peripheral retinal location.

The image quality can also be improved by reducing coma at theperipheral retinal location. The oblique angle can be between about 1degree and about 25 degrees. The peripheral retinal location can bedisposed at an eccentricity of about 1 degree to about 25 degrees withrespect to the fovea in the horizontal or the vertical plane. Forexample, the peripheral retinal location can be disposed at aneccentricity between about 7 degrees and about 13 degrees in thehorizontal plane. As another example, the peripheral retinal locationcan be disposed at an eccentricity between about 1 degree and about 10degrees in the vertical plane. At least one of the surfaces of the opticcan be aspheric. At least one of the surfaces of the optic can be atoric surface, a higher order aspheric surface, an aspheric Zernikesurface or a Biconic Zernike surface. An image formed by the combinationof the optic, an existing lens in the patient's eye and the cornea atthe peripheral retinal location can have a modulation transfer function(MTF) of at least 0.2 (e.g., at least 0.3, at least 0.4, at least 0.5.at least 0.6, at least 0.7, at least 0.8, at least 0.9 or values therebetween) for a spatial frequency of 30 cycles/mm for both the tangentialand the sagittal foci. An image formed by the combination of the optic,an existing lens in the patient's eye and the cornea at the fovea canhave a MTF of at least 0.2 (e.g., at least 0.3, at least 0.4, at least0.5. at least 0.6, at least 0.7, at least 0.8, at least 0.9 or valuesthere between) for a spatial frequency of 100 cycles/mm for both thetangential and the sagittal foci. The optic has an optical axis thatintersects the first and the second surface. A thickness of the opticalong the optical axis can be between about 0.1 mm and about 0.9 mm. Invarious implementations, a thickness of the optic along its periphery(or edge thickness) can vary and is not constant. The optic can besymmetric or asymmetric about the optical axis. The optic can beconfigured to be implanted between the iris and the existing lens. Theexisting lens can be configured to provide good image quality at thefovea.

In various implementations, both the surfaces of the optic can beconcave or convex. In some implementations, one surface can be convexand the other can be concave. In some implementations, one surface canbe convex or concave and the other can be planar. In variousimplementations, the optic can include diffractive features, prismaticfeatures, echelletes, etc.

Another aspect of the subject matter described in this disclosure can beimplemented in a method of designing an optic configured to be implantedin a patient's eye. The method comprises determining a surface profileof a first surface of the optic and determining a surface profile of asecond surface of the optic. The first and second surfaces of the opticcan be configured such that the optic has an optical power that reducesoptical errors in an image produced at a peripheral retinal locationdisposed at a distance from the fovea. The image can be produced byfocusing light incident on the patient's eye at an oblique angle withrespect to an optical axis intersecting the patient's eye at theperipheral retinal location by a combination of the optic, an existinglens and a patient's cornea.

The optical power of the optic that reduces optical errors at theperipheral retinal location can be obtained from a measurement of anaxial length along an axis which deviates from the optical axis andintersects the retina at the peripheral retinal location. In someimplementations, the optical power of the optic that reduces opticalerrors at the peripheral retinal location can be obtained from anestimate of an axial length along an axis which deviates from theoptical axis and intersects the retina at the peripheral retinallocation, the estimate based on measured ocular characteristics of thepatient obtained using a diagnostic instrument. The measured ocularcharacteristics can include axial length along the optical axis, cornealpower based at least in part on measurements of topography of thecornea, pre-operative refractive power and other parameters. The imageproduced at the peripheral retinal location can have reduced peripheralastigmatism and/or coma.

Another aspect of the subject matter disclosed herein can be implementedin a method of selecting an intraocular lens (IOL). The method comprisesobtaining at least one characteristic of the patient's eye using adiagnostic instrument; and selecting an IOL having an optical power thatreduces optical errors in an image produced at a peripheral retinallocation of the patient's eye disposed at a distance from the fovea. Theimage is produced by focusing light incident on the patient's eye at anoblique angle with respect to an optical axis intersecting the patient'seye at the peripheral retinal location by a combination of the optic, anexisting lens and the patient's cornea. The optical power of the IOL iscalculated and/or optimized based on the obtained characteristic. Theimage can have reduced coma and/or astigmatism. The oblique angle can bebetween about 1 degree and about 25 degrees. The IOL can be configuredsuch that the image has a modulation transfer function (MTF) of at least0.3 for a spatial frequency of 30 cycles/mm for both tangential andsagittal foci.

The obtained characteristic can include at least one of axial lengthalong the optical axis of the patient's eye, corneal power based atleast in part on measurements of topography of the cornea, an axiallength along an axis which deviates from the optical axis and intersectsthe retina at the peripheral retinal location, a shape of the retina ora measurement of optical errors at the peripheral retinal location. Insome implementations, the optical power can be obtained from an estimateof an axial length along an axis which deviates from the optical axisand intersects the retina at the peripheral retinal location. Theestimate can be based on the axial length along the optical axis of thepatient's eye and corneal power.

At least one of the surfaces of the first viewing element or the secondviewing element can be a toric surface, an aspheric surface, a higherorder aspheric surface, an aspheric Zernike surface or a Biconic Zernikesurface. At least one of the surfaces of the first viewing element orthe second viewing element can include a redirecting element. Theredirecting element can have a tailored slope profile as discussedherein. The redirecting element can include a diffractive feature and/ora prismatic feature.

Various implementations disclosed herein are directed towards anintraocular device (e.g., an intraocular lens, an ophthalmic solution, alaser ablation pattern, etc.) that improves visual acuity and contrastsensitivity for patients with central visual field loss, taking intoaccount visual field, distortion or magnification of the image. Thedevice can be configured to improve visual acuity and contrastsensitivity for patients with AMD through correction of the opticalerrors for the still healthy retina that the patient uses for viewing.The device can be configured to correct peripheral errors of the retinawith or without providing added magnification. The device can beconfigured to correct peripheral errors of the retina either withoutfield loss or in combination with magnification. The device can beconfigured to include a near vision zone. The device can be configuredto include multiple optical zones with add power. In variousimplementations, wherein the device is configured to focus lightincident in a large patch including a plurality of angles of incidenceis focused in a relatively small area of the retina such that the imagehas sufficient contrast sensitivity. In various implementations, lightincident from a plurality of angles of incidence are focused by thedevice as an extended horizontal reading zone above or below the fovea.In various implementations, light incident from a plurality of angles ofincidence are focused by the device in an area surrounding the fovea andextending upto the full extent of the peripheral visual field. Invarious implementations, the device is configured to provide sufficientcontrast sensitivity for light focused at the fovea for patients withearly stages of macular degeneration.

Various implementations of the device can include a redirection elementthat is configured to redirect incident light towards a peripheralretinal location. Various implementations of the device can includesymmetric lenses surfaces with aspheric surfaces. Variousimplementations of the device can include asymmetric lenses surfaceswith aspheric surfaces. Various implementations of the device caninclude asymmetric/symmetric lenses surfaces with aspheric surfaceshaving curvatures such that when implanted in the eye a distance betweenthe anterior surface of the lens and the pupil is between 2 mm and about4 mm and the image formed at a peripheral retinal location at aneccentricity between 7-13 degrees has an average MTF greater than 0.2for a spatial frequency of about 30 cycles/mm. The aspheric surfaces invarious implementations the device can include higher order asphericterms. In various implementations, the device can include a symmetricoptical element with a first surface and a second surface intersected byan optical axis. The thickness of the device along the optical axis canvary between 0.5 mm and about 2.0 mm. The first and the second surfacescan be aspheric. In various implementations, the aspheric surfaces caninclude higher order aspheric terms.

In various implementations, the device can be configured as a piggybacklens that can be provided in addition to an existing lens that isconfigured to provide good foveal vision. The piggyback lens can besymmetric or asymmetric. The piggyback lens can be configured to beimplanted in the sulcus or in the capsular bag in front of the existinglens.

In various implementations, the device can be configured as a dual opticintraocular lens having a first lens and a second lens. One or bothsurfaces of the first and the second lens can be aspheric. In variousimplementations, one or both surfaces of the first and the second lenscan include higher order aspheric terms. In various implementations ofthe dual optic intraocular lens, the optic proximal to the closer to thecornea can have a high positive power and can be configured to be movedeither axially in response to ocular forces to provide accommodation. Invarious implementations of the device described herein, the refractivepower provided by optic can be changed in response to ocular forces. Thechange in the refractive power can be brought about through axialmovement or change in the shape of the optic. Various implementations ofthe device described herein can include a gradient index lens. One ormore surfaces of the optics included in various implementations of thedevice described herein can be diffractive to provide near vision. Theoptical zones of various implementations of the device described hereincan be split for different retinal eccentricities.

Another aspect of the subject matter disclosed herein includes a powercalculation diagnostic procedure that measures corneal topography, eyelength, retinal curvature, peripheral eye length, pupil position,capsular position, or any combination thereof in order to determinecharacteristic of the intraocular lens device that improves visualacuity and contrast sensitivity for patients with central visual fieldloss.

Implementations of intraocular devices described herein can include oneor more optics with a large optical zone. The implementations ofintraocular devices described herein are configured to focus obliquelyincident light in a location of the peripheral retina at an eccentricitybetween about 5-25 degrees (e.g., eccentricity of 10 degrees,eccentricity of 15 degrees, eccentricity of 20 degrees, etc.). Forpatient with a well-developed preferred retinal location (PRL), variousimplementations of the intraocular device can be configured to focusincident light at the PRL. For patients without a well-developed PRL,the implementations of intraocular device described herein can help inthe formation of the PRL.

This disclosure also contemplates the use of diagnostic devices todetermine a region of the peripheral retina which provides the bestvision, determining the power of the intraocular device at variouslocations within the region of the peripheral retina and determining anintraocular device that would correct optical errors including defocus,astigmatism, coma, spherical aberration, chromatic aberration(longitudinal and transverse) at the region of the peripheral retina.When determining the intraocular device that would correct opticalerrors at the region of the peripheral retina, different figures ofmerit can be used to characterize the optical performance of differentconfigurations of the intraocular device and the intraocular device thatprovides the best performance can be selected. The different figures ofmerit can include MTF at spatial frequencies appropriate for the retinalareas, weighting of retinal areas, neural weighting, and weighting ofnear vision function.

The methods and systems disclosed herein can also be used to customizeIOLs based on the geometry of a patient's retina, the extent of retinaldegeneration and the geometry and condition of other structures in thepatient's eye. Various embodiments described herein can also treat otherconditions of the eye such as cataract and correct for presbyopia,myopia and/or astigmatism in addition to improving visual acuity and/orcontrast sensitivity of peripheral vision.

The methods and systems described herein to focus incident light at aregion of the peripheral retina around the fovea can also be applied tospectacle lenses, contact lenses, or ablation patterns for lasersurgeries (e.g., LASIK procedures).

Details of one or more implementations of the subject matter describedin this specification are set forth in the accompanying drawings and thedescription below. Other features, aspects, and advantages will becomeapparent from the description, the drawings, and the claims. Note thatthe relative dimensions of the following figures may not be drawn toscale.

BRIEF DESCRIPTION OF THE DRAWINGS

Example implementations disclosed herein are illustrated in theaccompanying schematic drawings, which are for illustrative purposesonly.

FIG. 1 is a diagram illustrating the relevant structures and distancesof the human eye.

FIG. 2 illustrates different regions of the retina around the fovea.

FIG. 3A-3D illustrate simulated vision with a central scotoma along withophthalmic device embodiments. A ray diagram lies to the right of eachsimulation.

FIG. 4A is a diagram of an eye implanted with an intraocular lens thatdeflects incident light to a preferred retinal location (PRL). FIG. 4Billustrates an image obtained by a PRL diagnostic device.

FIG. 5A illustrates an implementation of a symmetric piggyback lens thatcan be placed in addition to an existing lens in the eye of a patientsuffering from AMD. FIG. 5B illustrates an implementation of anasymmetric piggyback lens that can be placed in addition to an existinglens in the eye of a patient suffering from AMD.

FIG. 5C-1 illustrates the surface profile of an implementation of thepiggyback lens having a first surface sag. FIG. 5C-2 illustrates thesurface profile of an implementation of the piggyback lens having asecond surface sag.

FIG. 5D shows a cross-section view of an eye with a central scotoma atthe fovea and implanted with an implementation of an optic. FIG. 5D-1and FIG. 5D-2 illustrate regions of peripheral retina where the opticcan improve image quality. FIG. 5E graphically illustrates the variationin image quality versus eccentricity for an implementation of an opticconfigured to improve image quality at a peripheral retinal location andan optic configured to improve image quality at the fovea.

FIG. 6 illustrates a computer simulation model of an asymmetric opticthat is included in a piggyback lens optically coupled with an existinglens in the eye of a patient.

FIG. 7A shows the modulation transfer function for an IOL that providesgood foveal vision at an eccentricity of 10 degrees. FIG. 7B shows themodulation transfer function provided by the asymmetric optic inconjunction with the existing lens and cornea at an eccentricity of 10degrees.

FIG. 8 illustrates a block diagram of an example IOL design system fordetermining properties of an intraocular lens configured to improveoverall vision where there is a loss of central vision.

FIG. 9 illustrates parameters used to determine an optical power of anIOL based at least in part on a location of a PRL in a patient.

FIG. 10A and FIG. 10B illustrate implementations of a method fordetermining an optical power of an IOL tailored to improve peripheralvision.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

It is to be understood that the figures and descriptions have beensimplified to illustrate elements that are relevant for a clearunderstanding of embodiments described herein, while eliminating, forthe purpose of clarity, many other elements found in typical lenses,lens systems and lens design methods. Those of ordinary skill in thearts can recognize that other elements and/or steps are desirable andmay be used in implementing the embodiments described herein.

The terms “power” or “optical power” are used herein to indicate theability of a lens, an optic, an optical surface, or at least a portionof an optical surface, to focus incident light for the purpose offorming a real or virtual focal point. Optical power may result fromreflection, refraction, diffraction, or some combination thereof and isgenerally expressed in units of Diopters. One of ordinary skill in theart will appreciate that the optical power of a surface, lens, or opticis generally equal to the refractive index of the medium (n) of themedium that surrounds the surface, lens, or optic divided by the focallength of the surface, lens, or optic, when the focal length isexpressed in units of meters.

The angular ranges that are provided for eccentricity of the peripheralretinal location in this disclosure refer to the visual field angle inobject space between an object with a corresponding retinal image on thefovea and an object with a corresponding retinal image on a peripheralretinal location.

FIG. 1 is a schematic drawing of a human eye 200. Light enters the eyefrom the left of FIG. 1, and passes through the cornea 210, the anteriorchamber 220, a pupil defined by the iris 230, and enters lens 240. Afterpassing through the lens 240, light passes through the vitreous chamber250, and strikes the retina, which detects the light and converts it toa signal transmitted through the optic nerve to the brain (not shown).The eye 200 is intersected by an optical axis 280. The optical axis 280can correspond to an imaginary line passing through the midpoint of thevisual field to the fovea 260. The visual field can refer to the areathat is visible to the eye in a given position. The cornea 210 hascorneal thickness (CT), which is the distance between the anterior andposterior surfaces of the center of the cornea 210. The corneal centerof curvature 275 can coincide with geometric center of the eye 200. Theanterior chamber 220 has an anterior chamber depth (ACD), which is thedistance between the posterior surface of the cornea 210 and theanterior surface of the lens 240. The lens 240 has lens thickness (LT)which is the distance between the anterior and posterior surfaces of thelens 240. The eye has an axial length (AXL) which is the distancebetween the center of the anterior surface of the cornea 210 and thefovea 260 of the retina, where the image is focused. The LT and AXL varyin eyes with normal accommodation depending on whether the eye isfocused on near or far objects.

The anterior chamber 220 is filled with aqueous humor, and opticallycommunicates through the lens 240 with the vitreous chamber 250. Thevitreous chamber 250 is filled with vitreous humor and occupies thelargest volume in the eye. The average adult eye has an ACD of about3.15 mm, although the ACD typically shallows by about 0.01 mm per year.Further, the ACD is dependent on the accommodative state of the lens,i.e., whether the lens 240 is focusing on an object that is near or far.

FIG. 2 illustrates different regions of the retina around the fovea 260.The retina includes a macular region 207. The macular region 207 has twoareas: central and peripheral. Light focused on the central areacontributes to central vision and light focused on the peripheral areacontributes to peripheral vision. The central region is used to viewobjects with higher visual acuity, and the peripheral region is used forviewing large objects and for capturing information about objects andactivities in the periphery, which are useful for activities involvingmotion and detection.

The macular region 207 is approximately 5.5 mm in diameter. The centerof the macular region 207 is approximately 3.5 mm lateral to the edge ofthe optic disc 205 and approximately 1 mm inferior to the center of theoptic disc 205. The shallow depression in the center of the macularegion 207 is the fovea 260. The fovea 260 has a horizontal dimension(diameter) of approximately 1.5 mm. The curved wall of the depressiongradually slopes to the floor which is referred to as the foveola 262.The diameter of the foveola 262 is approximately 0.35 mm. The annularzone surrounding the fovea 260 can be divided into an inner parafovealarea 264 and an outer perifoveal area 266. The width of the parafovealarea 264 is 0.5 mm and of the perifoveal area 266 is 1.5 mm.

For the general population incident light is focused on the fovea 260.However, in patients suffering from AMD, a scotoma develops in thefoveal region which leads to a loss in central vision. Such patientsrely on the region of the peripheral retina around the fovea (e.g., themacular region 207) to view objects. For example, patients with AMD canfocus incident light on the PRL either by using a magnifying lens thatenlarges the image formed on the retina such that a portion of the imageoverlaps with a portion of the peripheral retina around the fovea or byrotating the eye or the head, thus using eccentric fixation such thatlight from the object is incident on the eye (e.g. at the cornea) atoblique angles and focused on a portion of the peripheral retina aroundthe fovea. The visual outcome for patients suffering from AMD can beimproved if optical errors resulting from oblique incidence of light orcoma are corrected. In some AMD patients, a portion of the peripheralretina around the fovea may have has greater visual acuity and contrastsensitivity compared to other portions of the peripheral retina. Thisportion is referred to as the preferred retinal location (PRL). Thevisual outcome for such patients may be improved if incident light werefocused at the PRL and the ophthalmic solutions corrected for opticalerrors at the PRL. This is explained in detail below.

Consider a patient suffering from AMD who desires to view a smart phoneat a normal distance (23 cm simulated here). In such a patient, thescotoma will block out the view as seen in FIG. 3A. One solution toimprove the visual outcome is to bring the object of interest closer tothe eye. This requires a magnifying glass to place the object opticallyat infinity. FIG. 3B illustrates the simulated view of a smart phoneviewed with the aid of a magnifying glass by a patient with a centralscotoma. The effect of the magnifying glass is to reduce the objectdistance and enlarge the size of the image formed on the retina suchthat it overlaps with a portion of the peripheral retina around thefovea. For the purpose of simulations, it is assumed that the magnifyingglass is used and hence the phone is assumed to be at a distance of 7.5cm. If the patient has cataract in addition to AMD and is implanted witha standard IOL, the peripheral errors will increase. FIG. 3C shows thesimulated view of a smart phone viewed by a patient implanted with astandard IOL and who also suffers from AMD. A comparison of FIGS. 3B and3C illustrates that the smart phone screen appears more blurry whenviewed by a patient implanted with a standard IOL due to the increase inperipheral errors.

Another solution to improve visual outcome is to utilize eccentricfixation to focus light from a visual interest on to a portion of theperipheral retina. FIG. 3D illustrates a simulated view of a smart phoneviewed using eccentric fixation to focus light from the smart phonescreen to a position on the peripheral retina located about 12.5 degreesaway from the fovea. Since, the image formed at the position on theperipheral retina is formed by light that is obliquely incident on theeye, optical errors arising from the oblique incidence of light maydegrade the visual quality. Accordingly, ophthalmic solutions that cancorrect optical errors arising from oblique incidence of light maybenefit AMD patients who rely on eccentric fixation to view objects.

As discussed above, some patients may have a well-developed PRL and mayprefer focusing incident light on the PRL. Such patients can benefitfrom an IOL that can focus light at the PRL instead of the fovea. FIG.4A is a diagram of the eye 200 implanted with an IOL 295 that deflectsincident light away from the fovea 260 to the PRL 290. For mostpatients, the PRL 290 is at a distance less than or equal to about 3.0mm from the fovea 260. Accordingly, the IOL 295 can be configured todeflect incident light by an angle between about 3.0 degrees and up toabout 30 degrees such that it is focused at a preferred location withina region at a distance of about 3.0 mm around the fovea 260. The IOL 295can be customized for a patient by determining the PRL for each patientand then configuring the IOL 295 to deflect incident light such that itis focused at the PRL. The method to find the PRL of any patient isbased on Perimetry. One perimetry method to locate the PRL is GoldmannPerimetry. The perimetry method to locate the PRL includes measuring thevisual field of a patient. For example, the patient can be asked tofixate on a cross and flashes of lights are presented at various partsin the field and the responses are recorded. From the recordedresponses, a map of how sensitive the peripheral retina is can becreated. The patient can be trained to consistently use the healthy andmore sensitive portions of the retina. The perimetry method can befurther enhanced by microperimetry, as used by e.g. the MacularIntegrity Assessment (MAIA) device, where the retina is tracked in orderto place the stimuli consistently and eye movement are accounted for.

The PRL can also be located subjectively, by asking the patient tofixate as they want into an OCT-SLO instrument. The instrument canobtain one or more images of the retina and determining which portionsof retina are used more than the other. One method of determining theportions of retina that are used more includes imposing the parts offixation onto an image of the retina. The OCT-SILO instrument can alsobe used to obtain normal images of the retina. FIG. 4B illustrates animage obtained using the perimetry method and the fixation method. FIG.4B shows a photo of the retina with a central scotoma 415. Thered-yellow-orange dots in the region marked 405 are the results of theperimetry. Perimetry results indicate that spots closer to the scotoma415 perform worse that spots farther away from the scotoma 415. The manysmall teal dots in the region marked 410 are the fixation points, andthe lighter teal point 420 is the average of the dots in the region 410.Based on the measurements, the PRL can be located at either point 420 orone some of the yellow points 425 a-425 d. Accordingly, an IOL 295 canbe configured to focus an image at one of the points 420 or 425 a-425 d.The determination of the PRL for a patient having both cataract and AMDcan be made by methods other than the methods described above.

Since, AMD patients rely on their peripheral vision to view objects,their quality of vision can be improved if optical errors in theperipheral vision are identified and corrected. Optical powercalculation for an IOL configured for foveal vision is based onmeasuring eye length and corneal power. However, power calculation foran IOL that focuses objects in an area around a peripheral retinallocation offset from the fovea can depend on the curvature of the retinaas well as the oblique astigmatism and coma that is associated with theoblique incidence of light in addition to the eye length and the cornealpower. Optical power calculation for an IOL that focuses objects in anarea around a peripheral retinal location can also depend on theposition of the IOL with respect to the iris and an axial length alongan axis which deviates from the optical axis and intersects the retinaat the peripheral retinal location

Methods that are used by an optometrist to measure optical power forspectacle lenses or contact lenses for non AMD patients with good fovealvision are not practical for measuring optical power for ophthalmicsolutions (e.g., IOL, spectacle lenses, contact lenses) for peripheralvision. Optometrists use various machines such as autorefractors, aswell as a method called subjective refraction wherein the patient readslines on the wall chart. The response is then used to gauge which triallenses to put in, and the lenses that give the best results are used.However, such a method is not practical to determine which ophthalmicsolution is best for a patient with AMD who relies on peripheral visionto view objects since, the performance estimates are rendered unreliableby the phenomenon of aliasing (a phenomenon which makes striped shirtslook wavy on some television sets with poor resolution), the difficultyof fixation and general fatigue associated with orienting the head/eyeto focus objects on the peripheral retina. Instead, the methods used toevaluate the optical power of ophthalmic solutions for AMD patients relyon peripheral wavefront sensors to estimate peripheral optical errors.Peripheral wavefront sensors illuminate a small patch of the PRL usinglasers and evaluate how the light reflected and coming out of the eye isshaped through an array of micro-lenses. For example, if the lightcoming out of the eye is converging, the patient is myopic at the PRL.

In various patients suffering from AMD as well as cataract, the naturallens 240 can be removed and replaced with the IOL 295, or implanted inthe eye 200 in addition to another IOL placed previously or at the sametime as the IOL 295. In some patients suffering from AMD, the IOL 295can be implanted in the eye 200 in addition to the natural lens 240. InFIG. 4A, the IOL 295 is implanted in the capsular bag. Where possible,the IOL 295 is placed as close to the retina as possible. However, inother implementations, the IOL 295 can be implanted within the capsularbag in front of another IOL or in front of the capsular bag. Forexample, the IOL 295 can be configured as an iris, sulcus or anteriorchamber implant or a corneal implant. By selecting an IOL 295 withappropriate refractive properties, the image quality at the PRL can beimproved.

The visual outcome at a peripheral retinal location is poor as comparedto the foveal visual due to a decreased density of ganglion cells at theperipheral retinal location and/or optical errors and artifacts thatarise due to oblique incidence of light (e.g., oblique astigmatism andcoma). Patients with AMD can receive substantial improvement in theirvision when optical errors at the peripheral retinal location arecorrected. Many of the existing embodiments of IOLs that are configuredto improve foveal visual outcome for a patient are not configured tocorrect for optical aberrations (e.g., coma, oblique astigmatism, etc.)in the image generated at the peripheral retinal location.

It is envisioned that the solutions herein can be applied to anyeccentricity. For example, in some patients, a location that is disposedat a small angle from the fovea can be used as the PRL while in someother patients, a location that is disposed at an angle of about 30degrees from the fovea can be used as the PRL.

Various embodiments of the IOLs disclosed herein are configured to focuslight at a location on the peripheral retina to produce good qualityimages, for example, images produced at the location on the peripheralretina can have a quality that is substantially similar to the qualityof images produced at the fovea. The images produced at the location onthe peripheral retina by the IOLs disclosed herein can have reducedartifacts from optical effects such as oblique astigmatism, coma orother higher order aberrations. Other embodiments are based on the factthat the location on the peripheral retina is not used in the same wayas the fovea. For example, it may be harder to maintain fixation on thePRL, so it may be advantageous to increase the area of the retina whereincident light is focused by the IOL in order to have sufficient visualacuity even when fixation is not maintained and/or when the eye is movedlinearly as in during reading. As such, the retinal area of interest cancover areas where the refraction differs substantially due todifferences e.g. in retinal curvature and oblique astigmatism. Variousembodiments of IOLs described herein can be used to direct and/or focuslight entering the eye along different directions at different locationsof the retina. Simulation results and ray diagrams are used to describethe image forming capabilities of the embodiments described herein.

As used herein, an IOL refers to an optical component that is implantedinto the eye of a patient. The IOL comprises an optic, or clear portion,for focusing light, and may also include one or more haptics that areattached to the optic and serve to position the optic in the eye betweenthe pupil and the retina along an optical axis. In variousimplementations, the haptic can couple the optic to zonular fibers ofthe eye. The optic has an anterior surface and a posterior surface, eachof which can have a particular shape that contributes to the refractiveproperties of the IOL. The optic can be characterized by a shape factorthat depends on the radius of curvature of the anterior and posteriorsurfaces and the refractive index of the material of the optic. Theoptic can include cylindrical, aspheric, toric, or surfaces with a slopeprofile configured to redirect light away from the optical axis and/or atight focus.

Piggyback IOL to Generate an Image at a location of the peripheralretina for AMD Patients

Many patients with AMD can be treated with a piggyback solution in whicha piggyback IOL is placed in addition to an existing lens. Some reasonsfor considering a piggyback solution are as follows: (i) for somepatients with AMD, a cataract surgery using a standard IOL can itselfbring substantial benefits. It is therefore possible that an eye careprofessional (e.g., a surgeon) would want to first try a standard IOLthat provides good foveal correction for a patient with AMD, and thenconsider providing additional correction with a piggyback lens if thevisual outcome provided by the standard IOL of the is not satisfactory;(ii) while comorbidity of AMD and cataract is relatively common, a largegroup of patients can develop AMD long after cataract surgery. Astandard IOL that provides good foveal vision may be already implantedin such patient's eye. Such patients may benefit from being implantedwith an additional piggyback lens that improves the visual outcome atone or more locations of the peripheral retina; (iii) the number ofstock keeping units of piggyback lenses can be smaller since the powerrange provided by piggyback lenses is smaller than for primary IOLimplantation. For example, piggyback lenses have optical power betweenabout −5 Diopters to about 5 Diopter while a primary IOL can haveoptical power between 5-34 Diopters.

As discussed above, the quality of an image generated by light that isincident obliquely on the eye of the patient and focused at a peripherallocation on the retina can be improved by providing a piggyback lens inaddition to an existing lens in the eye. The existing lens can be an IOL(e.g., standard IOL) that provides good foveal vision and/or the naturallens. The piggyback lens can be placed between the pupil and theexisting lens. For example, the piggyback lens can be fitted onto anexisting IOL, inserted into the capsular bag of the eye of the patientin front of an existing IOL and/or the natural lens, or inserted betweenthe iris and the capsular bag into the sulcus. In variousimplementations, the piggyback lens can be configured as a multifocallens with different optical zones providing different add power. Invarious implementations, the piggyback lens can include filters and/orcoatings to absorb short wavelengths that can damage the retina further.

The implementations of piggyback lenses described in this disclosureinclude an optic that can correct either lower order errors (e.g. sphereand cylinder), higher order aberrations (e.g., coma, trefoil) or bothresulting from the oblique incidence of light in the image formed at alocation of the peripheral retina. The implementations of piggybacklenses described in this disclosure can also configured to correct forperipheral astigmatism arising from the oblique incidence of light inthe image formed at a location of the peripheral retina. The opticincluded in the implementations of piggyback lens described herein has afirst surface facing the cornea and a second surface opposite the firstsurface and facing the retina. The optic is associated with an opticalaxis that passes through the geometrical center of the optic and joinsthe centers of curvature of the first and second surfaces. Variousimplementations of the piggyback lenses described herein can includeoptics that are symmetric about the optical axis such that the imagequality in a region around the optical axis is uniform. However, in someimplementations of the piggyback lenses described herein can includeoptics that are asymmetric about the optical axis such that the imagequality in a particular location with respect to the optical axis isbetter than the image quality at a different location.

The first and/or the second surface can be spheric, aspheric, biconic,conic, toric, etc. The first and/or the second surface can be describedmathematically by a polynomial function in either Cartesian or polarcoordinates. For example, the first and/or the second surface can bemathematically described by a polynomial function represented byequation (1) below:

$\begin{matrix}{z = {\frac{{cr}^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)c^{2}r^{2}}}} + {\sum\limits_{i = 1}^{8}\; {\alpha_{i}r^{2i}}} + {\sum\limits_{i = 1}^{N}\; {A_{i}{Z_{i}\left( {\rho,\varphi} \right)}}}}} & (1)\end{matrix}$

where z is the sag of the surface, c is the curvature of the surface, rthe radial distance from the optical axis 515, k the conic constant, αthe aspheric coefficients, A are the Zernike coefficients and Z are theZernike polynomials. The fifth and sixth Zernike coefficient A₅ and A₆correspond to the astigmatic terms and the seventh and eighth Zernikecoefficients A₇ and A_(g) order correspond to the coma term. In variousimplementations, the first and/or second surface can be described byaspheric coefficients including upto eighth order aspheric coefficients.In some implementations, the first and/or second surface can bedescribed by aspheric coefficients including aspheric coefficients withorder less than eight (e.g., 2, 4, or 6). In some implementations, thefirst and/or second surface can be described by aspheric coefficientsincluding aspheric coefficients with order greater than eight (e.g., 10,12 or 14). Alternatively, the first and/or second surface can bedescribed by up to 34 Zernike polynomial coefficients. In someimplementations, the first and/or second surface can be described byless than 34 Zernike coefficients. In some implementations, the firstand/or second surface can be described by more than 34 Zernikecoefficients. Additionally, the first and or second surface can bedescribed as a combination of these aspheric and Zernike coefficients.Lenses including aspheric surfaces and other complex surfaces are alsodescribed in U.S. application Ser. No. ______, filed concurrentlyherewith on Mar. 10, 2015, titled “INTRAOCULAR LENS THAT IMPROVESOVERALL VISION WHERE THERE IS A LOCAL LOSS OF RETINAL FUNCTION,”Attorney Docket No. AMOLNS.055A4, which is incorporated by referenceherein in its entirety. Additional implementations of dual optic lensesare also described in U.S. application Ser. No. ______, filedconcurrently herewith on Mar. 10, 2015, titled “INTRAOCULAR LENS THATIMPROVES OVERALL VISION WHERE THERE IS A LOCAL LOSS OF RETINALFUNCTION,” Attorney Docket No. AMOLNS.055A4, which is incorporated byreference herein in its entirety.

The first and the second surface of the piggyback lens can be configuredsuch that the piggyback lens is a meniscus shaped lens with edges benttowards the existing lens (e.g., standard IOL or the natural lens). Forexample, the first and the second surface of can be configured such thatthe surface of the piggyback lens adjacent the existing lens (e.g.,standard IOL or the natural lens) is convex. In some implementations,the surface of the optic of the piggyback lens adjacent the existinglens (e.g., standard IOL or the natural lens) can have a shape and sizeidentical to the corresponding surface of the existing lens. Thethickness along the optical axis for various implementations of theoptic of the piggyback lenses disclosed herein can be less than 1.0 mm.For example, the thickness of the optic along the optical axis can varybetween about 0.25 mm and about 0.4 mm, about 0.3 mm and about 0.5 mm,about 0.4 mm and about 0.6 mm, about 0.5 mm and about 0.7 mm, about 0.6mm and about 0.8 mm, about 0.7 mm and about 0.9 mm, about 0.9 mm andabout 1.0 mm, or values therebetween. In various implementations, thethickness along the periphery or the edge of the optic can benon-uniform.

The characteristic of the first and second surface of the optic, thethickness of the optic, etc. can be designed such that the piggybacklens in conjunction with the cornea and the existing lens (e.g., naturallens or standard IOL) can focus light incident on the eye (e.g., at thecornea) at oblique angles (e.g., between about −25 degree and about +25degrees with respect to the optical axis of the eye) at a location onthe peripheral retina around the fovea. For example, the piggyback lensin conjunction with the cornea and the existing lens can be configuredto focus obliquely incident light of a large patch around a location onthe peripheral retina. Without any loss of generality, a large patchconfiguration refers to configuration when the isoplantic patch islarge. In other words, there are a large range of angles (patch) ofincidence that are focused at corresponding retinal locations in a smallarea such that any individual point of the image is sharply focused. Asanother example, various implementations of the piggyback lenses can beconfigured such that in conjunction with an existing lens and thecornea, obliquely incident light is focused in an area that is disposedwithin a cone having a semi angle of about 3-6 degrees about a locationof the peripheral retina. As discussed above, the piggyback lens can beconfigured to provide optical refractive power between about −5.0Diopter and +5.0 Diopter. In some implementations, the piggyback lenscan be configured as a multifocus lens capable of providing add power inthe range of 0.5-3.0 Diopter. In various implementations, the piggybacklens in combination with the existing lens can be configured to correctfor corneal astigmatism. In various implementations, the piggyback lenscan be configured to provide astigmatic power between 0.5 Diopter andabout 6.0 Dipoters.

FIGS. 5A and 5B illustrate different implementations of an optic that isincluded in a piggyback lens. The implementation of optic 500 aillustrated in FIG. 5A is symmetric about the optical axis 515, whilethe implementation of the optic 500 b illustrated in FIG. 5B isasymmetric about the optical axis 515. The thickness of the optic 500 aillustrated in FIG. 5A along the periphery can be uniform or constant.In contrast, the thickness of the optic 500 b illustrated in FIG. 5Balong the periphery can be non-uniform or not constant. As discussedabove, piggyback lenses including optics 500 a and 500 b are configuredto be inserted between the pupil/iris of the patient and an existinglens (e.g., a natural lens or a standard IOL). For example, thepiggyback lenses can be implanted in the capsular bag or the sulcus ofthe patient's eye. Accordingly, the thickness of the optics 500 a and500 b is less than 1.0 mm and preferably between about 0.25 mm and about0.5 mm (e.g., 0.3 mm, 0.35 mm, 0.4 mm, etc.). The piggyback lenses canbe implanted in the patient's eye such that the optical axis 515 of theoptic 500 a or 500 b is coincident with the optical axis 280 of thepatient's eye. The piggyback lenses 500 a and 500 b can be implanted inthe patient's eye such that the optical axis 515 of the optic 500 a or500 b is offset and/or tilted with respect to the optical axis 280 ofthe patient's eye.

The optic 500 a and 500 b have a first convex surface 505 and a secondconvex surface 510 opposite the first surface 505. Accordingly, theimplementations of the piggyback lenses including optics 500 a or 500 bcan be referred to as a meniscus lens. Although in the illustratedimplementations, the first surface 505 and the second surface 510 areconvex, in other implementations, the first and/or second surface 505and 510 can be planar or concave. In various implementations, the optics500 a/500 b can be configured as a reversed meniscus, a biconvex lens ora biconcave lens. The shape and curvature of the first and/or secondsurface 505 and 510 can be selected based on the patient's visualrequirements as well the patient's ocular characteristics and theoptical and physical characteristics of the existing lens.

In various implementations, the optics 500 a and 500 b can be configuredsuch that the refractive properties of optics 500 a and 500 b can bechanged in response to the eye's natural process of accommodation. Forexample, the optics 500 a and 500 b can comprise a deformable materialthat can compress or expand in response to ocular forces applied by thecapsular bag and/or the ciliary muscles. For example, the optics 500 aand 500 b can be configured to change their shape in response to ocularforces in the range between about 1 gram to about 10 grams, 5 to 10grams, 1 to 5 grams, about 1 to 3 grams or values therebetween. Invarious implementations, the optics 500 a and 500 b can comprisematerials such as acrylic, silicone, polymethylmethacrylate (PMMA),block copolymers of styrene-ethylene-butylene-styrene (C-FLEX) or otherstyrene-base copolymers, polyvinyl alcohol (PVA), polystyrenes,polyurethanes, hydrogels, etc. The optics 500 a and 500 b can comprisestructures and materials that are described in U.S. Publication No.2013/0013060 which is incorporated by reference herein in its entirety.

Although not illustrated, the piggyback lenses 500 a and 500 b can beprovided with a haptic that holds the piggyback lens in place whenimplanted in the eye. The haptic can comprise a biocompatible materialthat is suitable to engage the capsular bag of the eye, the iris 230,the sulcus and/or the ciliary muscles of the eye. For example, thehaptic can comprise materials such as acrylic, silicone,polymethylmethacrylate (PMMA), block copolymers ofstyrene-ethylene-butylene-styrene (C-FLEX) or other styrene-basecopolymers, polyvinyl alcohol (PVA), polystyrene, polyurethanes,hydrogels, etc. In various implementations, the haptic can include a oneor more arms that are coupled to the optics 500 a/500 b. For example,the haptic can be configured to have a structure similar to thestructure of the biasing elements disclosed in U.S. Publication No.2013/0013060 which is incorporated by reference herein in its entirety.In various implementations, the haptic can include one or more arms thatprotrude into the optic 500 a/500 b. In various implementations, thehaptic can be configured to move the optic 500 a/500 b along the opticalaxis of the eye in response to ocular forces applied by the capsular bagand/or the ciliary muscles. For example, the haptic can include one ormore hinges to facilitate axial movement of the optic. As anotherexample, the haptic can include springs or be configured to bespring-like to effect movement of the optic 500 a/500 b. In this manner,the distance between the piggyback lens and the existing lens (e.g.,natural lens or a standard IOL) can be varied in response to ocularforces to provide vision over a wide range of distances. A piggybacklens that is configured to change the axial position of the optic and/orshape and size of the optic in response to ocular forces applied by thecapsular bag and/or ciliary muscles can be referred to as anaccommodating lens.

FIGS. 5C-1 and 5C-2 illustrate the surface profiles in one of themeridians of the asymmetric optic 500 b that can be included in animplementation of a piggyback lens. Without any loss of generality, thefirst surface 505 of the optic 500 b illustrated in FIG. 5B can have aprofile as shown in FIG. 5C-1 and the second surface 510 can have aprofile as shown in FIG. 5C-2. The first and the second surfaces 505 and510 can be mathematically described by a polynomial equation similar toequation (1) above. The surface sag of the first surface 505 and thesecond surface 510 can be varied by selecting different values of thecurvature, conic constant, and other parameters. In variousimplementations, the surfaces can be described by other polynomialequations different from equation (1).

As discussed herein, the optic 500 a/500 b is configured such that whenoptically coupled with the cornea and an existing lens in the patient'seye (e.g., a natural lens or a standard IOL) light incident on the eye(e.g., at the cornea) at oblique angles to the optical axis 280 of theeye is focused on a location of the peripheral retina away from thefovea. The light can be incident in the vertical field of view or thehorizontal field of view. For example, the piggyback lens in conjunctionwith the cornea and an existing lens can be configured to focus lightincident at oblique angles between about 5 degrees and about 30 degreeswith respect to the optical axis 280 of the eye, between about 10degrees and about 25 degrees with respect to the optical axis 280 of theeye, between about 15 degrees and about 20 degrees with respect to theoptical axis 280 of the eye, or there between at a location on theperipheral retina away from the fovea.

The optic 500 a/500 b can also be configured such that when opticallycoupled with the cornea and an existing lens in the patient's eye (e.g.,a natural lens or a standard IOL) light incident on the eye (e.g., atthe cornea) along a direction parallel to the optical axis is focused onthe fovea for those patients with early AMD who still have some fovealvision. For example, some patients may have parts of the fovea coveredby a scotoma instead of a central scotoma. Such patients may have someresidual foveal vision and can benefit from incident light being focusedat the fovea by the combination of the piggyback lens and the exitinglens. Additionally, the piggyback lens and/or the existing lens in thepatient's eye can also be configured to accommodate to focus objectslocated at different distances on to the retina (e.g., at a location onthe periphery of the retina and/or the fovea) in response to ocularforces exerted by the capsular bag and/or ciliary muscles.

As discussed above, the implementations of the optic 500 a/500 bdescribed herein can be configured to correct lower order errors (e.g.sphere and cylinder), higher order aberrations (e.g., coma, trefoil) orboth resulting from the oblique incidence of light in the image formedat a location of the peripheral retina. The optic 500 a/500 b can alsoconfigured to correct for peripheral astigmatism arising from theoblique incidence of light in the image formed at a location of theperipheral retina. The characteristic of the surfaces 505 and/or 510 ofthe optic 500 a/500 b, the thickness of the optic 500 a/500 b, thedistance between the optic 500 a/500 b and the cornea, the distancebetween the optic 500 a/500 b and the existing lens, etc. can bedesigned such that the piggyback lens including the optic 500 a/500 b incombination with the cornea and the existing lens can focus lightincident on the eye at a plurality of oblique angles (e.g., betweenabout −25 degree and about +25 degrees with respect to the optical axis280 of the eye) in an area around a location on the peripheral retinaspaced away from the fovea with sufficient visual contrast. This isexplained in further detail below with respect to FIG. 5D.

FIG. 5D shows a cross-section view of an eye with a central scotoma atthe fovea 260 and implanted with a piggyback lens including an optic 500similar to optic 500 a illustrated in FIG. 5A or optic 500 b illustratedin FIG. 5B. The existing lens and the cornea are not illustrated. Lightfrom an object is incident in a range of oblique angles between θ₁ andθ₂ with respect to the optical axis 280 and is focused by thecombination of the optic 500, the existing lens and the cornea in anarea 525 disposed around a location 520 on the peripheral retinadisposed away from the fovea 260. For most patients θ₁ can be between 1degree and 5 degrees and θ₂ can be between 10 degrees and 35 degrees.The location 520 can be located at a distance r from the fovea 260 alonga direction that makes an angle θ₃ with respect to a tangential line 530intersecting the retina at the fovea 260 and lying in the verticalplane. Although, not shown in FIG. 5D, the location 520 can be locatedat a distance r from the fovea 260 along a direction that makes an angleθ₄ with respect to a tangential line (not shown) intersecting the retinaat the fovea 260 and lying in the horizontal plane. The angles θ₃ and θ₄can have a value greater than or equal to 0 degrees and less than 30degrees. The distance r can have a value between about 0.5 mm and about4 mm.

The area 525 can be described as the region between a first region whichis the base of a cone having a semi angle of θ₁ degrees with respect tothe optical axis 280 and a second region which is the base of a conehaving a semi angle of about θ₂ degrees with respect to the optical axis280. Accordingly, the angular width of the area 525 is given by (θ₂−θ₁).For most patients, the angular width of the area 525 can be betweenabout 5 degrees and about 30 degrees. Without any loss of generality,the area 525 can include locations that are within about 2-5 mm from thefovea 260. The area 525 can have an angular extent Δθε_(1h) in thehorizontal plane and an angular extent Δθ_(1v) in the vertical plane. Invarious implementations, the angular extent Δθ_(1v) can be zero orsubstantially small such that the area 525 is a horizontal line above orbelow the fovea 260. Alternately, the angular extent Δθ_(1h) can be zeroor substantially small such that the area 525 is a vertical line to theleft or the right of the fovea 260. In some embodiments, the angularextent Δθ_(1v) and the angular extent Δθ_(1h) can be equal such that thearea 525 is circular. In some other implantations, the angular extentΔθ_(1h) and the angular extent Δθ_(1h) can be unequal such that the area525 is elliptical. In various implementations, the angular extentΔθ_(1h) and the angular extent Δθ_(1h) have values such that the area525 includes the fovea 260. However, in other implementations, theangular extent Δθ_(1h) and the angular extent Δθ_(1h) can have valuessuch that the area 525 does not include the fovea 260.

As discussed herein, the piggyback lens can be symmetric such that theimage quality in an annular region around the fovea is uniform. Such alens system can be used by patients who do not have a well-developed PRLand who can orient their eyes and/or heads to select the position thataffords the best visual quality. The annular region can be between afirst region and a second region. The first region can be the base of acone having a semi angle of θ₁ degrees with respect to the optical axis280 and the second region can be the base of a cone having a semi angleof about θ₂ degrees with respect to the optical axis 280. Accordingly,the angular width of the annular region is given by (θ₂−θ₁). For mostpatients θ₁ can be between 3 degrees and 5 degrees and θ₂ can be between20 degrees and 35 degrees. Accordingly, for most patients, the angularwidth of the annular region can be between about 10 degrees and about 30degrees. Without any loss of generality, the annular region can includelocations that are within about 3-5 mm from the fovea. Alternately, thepiggyback lens can be asymmetric such that the image quality isoptimized for a certain location of the peripheral retina (e.g., thePRL). Such an IOL system can be used by patients who do have awell-developed PRL. The PRL can be located within an annular regionaround the fovea having an angular width between about 10-30 degrees.The PRL can be located at a distance between about 3-5 mm from thefovea. The PRL can be determined using the methods discussed above withreference to FIG. 4B.

Generally, patients with AMD experience greater improvement in theirvision when refractive errors arising from the oblique astigmatism andcoma are corrected for image formed at a location in the peripheralretina than patients without AMD at similar retinal eccentricities.Accordingly, the piggyback lens is configured such that the refractiveerrors due to relative peripheral defocus, oblique astigmatism and comain an image produced at a location of the peripheral retina by thecombination of the piggyback lens and the existing lens are reduced.Additionally, the piggyback lens can also be configured to provide goodvisual quality at the fovea in conjunction with the existing lens forthose patients who have early stage AMD. In contrast to optics and IOLsthat are configured to improve image quality at the fovea, the piggybacklens including the optic 500 a/500 b in combination with the existinglens and the cornea is configured to improve image quality in a regionof the peripheral retina that is offset from the fovea. For example, thepiggyback lens including the optic 500 a/500 b in combination with theexisting lens and the cornea can be configured to improve image qualityin an annular zone surrounding the fovea 260 as shown in FIG. 5D-1. Theannular zone can include an area 545 between an inner periphery 535surrounding the fovea and an outer periphery 540 surrounding the fovea260. The inner periphery 535 can include retinal locations at aneccentricity between about 1 degree and about 10 degrees. Without anyloss of generality, as used herein, the term eccentricity refers to theangle between a normal to the retina at the location of interest and theoptical axis of the eye which intersects the retina at the fovea.Accordingly, the fovea is considered to have an eccentricity of about 0degrees. The outer periphery 540 can include retinal locations at aneccentricity between about 3 degrees and about 25 degrees. Although inFIG. 5D-1 the piggyback lens including the optic 500 a/500 b incombination with the existing lens and the cornea is not configured toimprove image quality in the foveal region, in various implementations,the area 545 in which the piggyback lens including the optic 500 a/500 bin combination with the existing lens and the cornea is configured toimprove image quality can extend to the foveal region and include thefovea 260 for patient who have residual foveal vision. In suchimplementations, the piggyback lens including the optic 500 a/500 b incombination with the existing lens and the cornea can be configured toprovide good image quality at the fovea as well as at peripheral retinallocations at an eccentricity between about 1 degree and about 25degrees. In various implementations, the region 545 can be symmetricabout the fovea 260. In some implementations, a projection of the region545 on a plane tangential to the retina at the fovea 260 can becircular, oval or any other shape.

As another example, the piggyback lens including the optic 500 a/500 bin combination with the existing lens and the cornea can be configuredto improve image quality in a region 548 surrounding a preferred retinallocation (e.g., location 520 as shown in FIG. 5D) offset from the foveaas shown in FIG. 5D-2. The preferred retinal location can be located atan eccentricity between about 1 degree and about 25 degrees. The region548 surrounding the preferred retinal location 520 can include retinallocations at an eccentricity between about 1 degree and about 25degrees.

The image quality at the region of the peripheral retina can be improvedby optimizing the image quality produced by the piggyback lens includingthe optic 500 a/500 b in combination with the existing lens and thecornea such that optical errors (e.g., peripheral astigmatism, coma,trefoil, etc.) are reduced at the peripheral retinal region. Forexample, the image quality at the peripheral retinal region can beincreased by correcting optical errors at the peripheral retinal region,correcting for corneal astigmatism at the peripheral retinal region,reducing optical errors resulting from oblique astigmatism at theperipheral retinal region, reducing coma at the peripheral retinalregion and/or reducing other higher order aberrations at the peripheralretinal region.

The improvement in the image quality at the peripheral retinal regionprovided by the system including the optic 500 a/500 b, the existinglens in the patient's eye and the patient's cornea can be measured usingdifferent figures of merit discussed below. One figure of merit that canbe used to measured image quality is the modulus of optical transferfunction (MTF) at one or more spatial frequencies which provides ameasure of contrast sensitivity or sharpness. The MTF for the systemincluding the optic 500 a/500 b, the existing lens in the patient's eyeand the patient's cornea is calculated for both sagittal rays andtangential rays originating from an object disposed with respect to theintersection of the optic and the optical axis of the eye. Accordingly,two MTF curves are calculated one for sagittal rays and the other fortangential rays. For an image to have good quality and sufficientcontrast sensitivity, the MTF for both the tangential rays and thesagittal rays should be above a threshold. The MTF is calculated forvarious off-axis positions of the object represented by coordinatesalong the x-direction and the y-direction in a Cartesian coordinatesystem in which the point of intersection of the optic and the opticalaxis of the eye is disposed at the origin of the Cartesian coordinatesystem and the optical axis is along the z-direction. In variousimplementations, the point of intersection of the optic and the opticalaxis of the eye can coincide with the geometric of the optic and/or thegeometric center of a surface of the optic.

The MTF of the system including the optic 500 a/500 b, the existing lensin the patient's eye and the patient's cornea refers to how much of thecontrast ratio in the object is preserved when the object is imaged bythe optic. A MTF of 1.0 indicates that the optic does not degrade thecontrast ratio of the object and MTF of 0 indicates that the contrastratio is degraded such that adjacent lines in the object cannot beresolved when the object is imaged by the optic. Accordingly, the MTF isa measure of contrast sensitivity or sharpness. Another figure of meritcan include average MTF for a range of retinal locations andeccentricities, either close to a single PRL or for multiple PRLs forthe patient, and with spatial frequencies chosen to match the retinalsampling. Other figures of merit can include area under the MTF curvefor different spatial frequencies, average MTF for a range of spatialfrequencies or combinations of the figures of merit listed here.

An optic (e.g., the optic 500 a/500 b) that is configured to improveimage quality in the peripheral retinal region can provide a MTF greaterthan a threshold value (MTF_(THR)) at one or more spatial frequenciesfor an image produced at the desired peripheral retinal region.Similarly, an optic that is configured to improve image quality in thefoveal region can provide a MTF greater than a threshold value(MTF_(THR)) at one or more spatial frequencies for an image produced atthe foveal region. The threshold value (MTF_(THR)) can be subjective andbe determined based on the patient's needs and ophthalmic condition. Forexample, some patients may be satisfied with an image quality having aMTF greater than 0.1 for spatial frequencies between 10 cycles/mm and 50cycles/mm. Some other patients may desire a MTF greater than 0.5 forspatial frequencies between 1 cycle/mm and 100 cycles/mm. Accordingly,the threshold MTF value (MTF_(THR)) can vary depending on the lensdesign and the patient's needs. The increase in MTF value can becorrelated with an improvement in the patient's ability to read variouslines in an eye chart. For example, without any loss of generality, anincrease in MTF from 0.7 to 0.8 can correspond to about 15% contrastsensitivity improvement, or 1 line of visual acuity (VA). Similarly, anincrease in MTF from 0.7 to 0.9 can correspond to about 30% increase incontrast sensitivity or 2 lines VA.

FIG. 5E which shows the variation in image quality versus eccentricityfor an implementation of an optic configured to improve image quality ata peripheral retinal region and an optic configured to improve imagequality at the fovea region. Curve 550 shows the variation of MTF versuseccentricity for an optic configured to improve image quality at aperipheral retinal region while curve 555 shows the variation of MTFversus eccentricity for an optic configured to improve image quality atthe foveal region. As shown in FIG. 5E the optic configured to improveimage quality at a peripheral retinal region provides a MTF greater thana threshold value (MTF_(THR)) at one or more spatial frequencies at aneccentricity between 1 degree and 25 degrees and −1 degree and −25degrees such that an image produced in the peripheral retinal region atan eccentricity between 1 degree and 25 degrees and −1 degree and −25degrees has sufficient contrast sensitivity. In various implementations,the optic may be configured to improve image quality at a peripheralretinal region at the expense of foveal vision. For example, the opticconfigured to improve image quality at a peripheral retinal region mayprovide a MTF less than the threshold value (MTF_(THR)) in the fovealregion (e.g., at an eccentricity between −1 degree and 1 degree). Incontrast, an optic configured to improve foveal vision will provide anMTF greater than the threshold value (MTF_(THR)) for an image producedin the foveal region. In some implementations, the optic configured toimprove image quality at a peripheral retinal region may also beconfigured to provide a MTF value greater than the threshold value(MTF_(THR)) at the foveal region as shown by curve 560.

One way to configure the piggyback lens including an optic similar tooptic 500 a/500 b to reduce optical errors at a peripheral retinalregion when combined with the cornea and an existing lens is todetermine the surface profiles of the first surface 505 and the secondsurface 510 that reduce optical errors due to oblique astigmatism andcoma at the peripheral retinal region when light incident on the eyeobliquely with respect to the optical axis 280 is focused by thecombination of the cornea, piggyback lens and the existing lens at theperipheral retinal region. Using a lens designing system various surfacecharacteristics of the first and/or second surface 505 and 510 of theoptic 500 a/500 b can be determined that reduce refractive errors at aperipheral location of the retina. The various surface characteristicscan include curvatures, surface sags, radius of curvatures, conicconstant, axial thickness, area of the optical zone, diffractivefeatures, echelletes and/or prismatic features provided with the optic,etc. In various implementations, a portion of the first surface 505and/or the second surface 510 can include redirecting elements similarto the prismatic features and/or diffractive features described in U.S.Provisional Application No. 61/950,757, filed on Mar. 10, 2014, titled“INTRAOCULAR LENS THAT IMPROVES OVERALL VISION WHERE THERE IS A LOSS OFCENTRAL VISION,” which is incorporated by reference herein in itsentirety. The redirecting elements can be configured to redirect lightincident on the eye along the optical axis and/or at an angle to theoptical axis to one or more locations on the retina.

The surface characteristics can be determined using an eye model that isbased on average population statistics. Alternately, the surfacecharacteristics can be determined by using an eye model that is specificto each patient and constructed using a patient's individual ocularcharacteristics. Some of the ocular characteristics that can be takeninto consideration when determining the characteristics of the surfacesof the optics 500 a/500 b can include corneal radius of curvature andasphericity, axial length, retinal curvatures, anterior chamber depth,expected lens position, location of image on the peripheral retina, sizeof the scotoma, optical and physical characteristics of the existinglens, peripheral aberrations, etc. Depending on the patient's needs, thefirst and/or the second surface 505, 510 of the optic 500 a/500 b can besymmetric or asymmetric and/or include higher (e.g., second, fourth,sixth, eighth) order aspheric terms. For example, the first and/or thesecond surface 505, 510 of the optic 500 a/500 b can be described by aZernike polynomial having eighth order Zernike coefficient. The firstand/or second surface 505, 510 of the optic 500 a/500 b can beparabolic, elliptical, a Zernike surface, an aspheric Zernike surface, atoric surface, a biconic Zernike surface, etc.

FIG. 6 illustrates a computer simulation model of an asymmetric optic605 that is included in a piggyback lens optically coupled with anexisting lens 610 in the eye of a patient. The optic 605 can be anasymmetric optic similar to the optic 500 b illustrated in FIG. 5B. Theoptic 605 has two complex surface 605 a and 605 b. The surfaces 605 aand 605 b can be compound Zernike surfaces, higher order asphericsurfaces, toric surfaces, etc. In various implementations, the surfaces605 a and 605 b can have a surface profile in one of the meridianssimilar to the surface profile shown in FIGS. 5C-1 and 5C-2. For thepurpose of simulation, the existing lens 600 is considered to be astandard 20.0 Diopter Tecnis IOL.

For the purpose of the simulation, the existing lens 600 is consideredto provide full foveal. The patient is considered to have developed AMDafter the existing lens 600 was implanted and has developed a preferredretinal locus (PRL) at an eccentricity of 10 degrees from the fovea.

FIG. 7A illustrates the modulus of the optical transfer function (MTF)at an eccentricity of 10 degrees for different spatial frequenciesbetween 0 cycles/mm and 30 cycles/mm. The MTF is calculated (orsimulated) for light incident in the tangential plane as well as thesagittal plane. The MTF can be calculated (or simulated) using anoptical simulation program such as, for example, OSLO, ZEMAX, CODE V,etc. As observed from FIG. 7A, the MTF at the PRL is less than 0.4 for aspatial frequency of 30 cycles/mm for tangential focus, while themodulus of the OTF is less than 0.9 for a spatial frequency of 30cycles/mm for sagittal focus. The patient can benefit from increase inthe modulus of OTF for at least the tangential focus. FIG. 7Billustrates the MTF at the PRL for different spatial frequencies between0 cycles/mm and 30 cycles/mm when the additional asymmetric optic 605 isprovided. From FIG. 7B, it is noted that the MTF for both tangential andsagittal foci is greater than 0.9 for spatial frequency of 30 cycles/mm.Accordingly, addition of the optic 605 can improve the image quality(e.g., contrast ratio of the image) at the PRL. In variousimplementations, piggyback lenses can be configured to provide a MTF ata spatial frequency of 30 cycles/mm of at least 0.5. For example,piggyback lenses can be configured to provide a MTF at a spatialfrequency of 30 cycles/mm greater than 0.5, greater than 0.6, greaterthan 0.7, greater than 0.8 and greater than 0.9 for eccentricitiesbetween about 7 degrees and 13 degrees from the fovea.

The piggyback lens can be configured to provide one of distance vision,near vision, or intermediate distance vision, distance vision and nearvision, distance vision and intermediate distance vision, near visionand intermediate distance vision or all. Although, the piggyback lens inthe above discussion was configured to increase the modulus of theoptical transfer function at a particular spatial frequency, in otherimplementations, the piggyback lens can be configured to increase otherfigures of merit, such as, for example, area under the MTF curve fordifferent spatial frequencies, average MTF for a range of spatialfrequencies, average MTF for a range of retinal locations andeccentricities, either close to a single PRL or for multiple PRLs forthe patient, and with spatial frequencies chosen to match the retinalsampling, or combinations of figures of merit listed here. For example,an implementation of a piggyback lens configured for reading can beconfigured to increase the average MTF for a range of spatialfrequencies and locations from 0.41 to 0.81.

It is conceived that the implementations of piggyback lenses that areconfigured to improve image quality at a peripheral retinal location incombination with an existing lens by correcting optical errors arisingfrom oblique incidence of light (e.g., oblique astigmatism and coma) canimprove the MTF by at least 5% (e.g., at least 10% improvement, at least15% improvement, at least 20% improvement, at least 30% improvement,etc.) at a spatial frequency of 30 cycles/mm for both tangential andsagittal foci at a peripheral retinal location at an eccentricitybetween about 1 degree and about 25 degrees with respect to the fovea ascompared to the MTF at a spatial frequency of 30 cycles/mm provided byan IOL that is configured to improve image quality at the fovea at thesame peripheral retinal location.

It is conceived that the implementations of piggyback lenses that areconfigured to improve image quality at a peripheral retinal location incombination with an existing lens by correcting optical errors arisingfrom oblique incidence of light (e.g., oblique astigmatism and coma) canprovide a MTF greater than 0.2 at a spatial frequency of 30 cycles/mmfor both tangential and sagittal foci, greater than 0.3 at a spatialfrequency of 30 cycles/mm for both tangential and sagittal foci, greaterthan 0.4 at a spatial frequency of 30 cycles/mm for both tangential andsagittal foci, greater than 0.5 at a spatial frequency of 30 cycles/mmfor both tangential and sagittal foci, greater than 0.6 at a spatialfrequency of 30 cycles/mm for both tangential and sagittal foci, greaterthan 0.7 at a spatial frequency of 30 cycles/mm for both tangential andsagittal foci, greater than 0.8 at a spatial frequency of 30 cycles/mmfor both tangential and sagittal foci or greater than 0.9 at a spatialfrequency of 30 cycles/mm for both tangential and sagittal foci at aperipheral retinal location between about 1 degree and about 25 degreeswith respect to the fovea.

The optic 500 a/500 b can have a clear aperture. As used herein, theterm “clear aperture” means the opening of a lens or optic thatrestricts the extent of a bundle of light rays from a distant sourcethat can imaged or focused by the lens or optic. The clear aperture canbe circular and specified by its diameter. Thus, the clear aperturerepresents the full extent of the lens or optic usable for forming theconjugate image of an object or for focusing light from a distant pointsource to a single focus or to a plurality of predetermined foci, in thecase of a multifocal optic or lens. It will be appreciated that the termclear aperture does not limit the transmittance of the lens or optic tobe at or near 100%, but also includes lenses or optics having a lowertransmittance at particular wavelengths or bands of wavelengths at ornear the visible range of the electromagnetic radiation spectrum. Insome embodiments, the clear aperture has the same or substantially thesame diameter as the first or second viewing element. Alternatively, thediameter of the clear aperture may be smaller than the diameter of thefirst or second viewing element. In various implementations of thepiggyback lenses system described herein the clear aperture of the optic500 a/500 b can have a dimension between about 3.0 mm and about 7.0 mm.For example, the clear aperture of the optic 500 a/500 b can be circularhaving a diameter of about 5.0 mm in various implementations of thepiggyback lenses.

The optic 500 a/500 b can include prismatic, diffractive elements,echelletes or optical elements with a gradient refractive index (GRIN)profile to provide a larger depth of field or near vision capability.The optic 500 a/500 b can include one or more apertures in addition tothe clear aperture to further enhance peripheral image quality.

The piggyback lenses described herein can use additional techniques toextend the depth of focus. For example, the optic 500 a/500 b caninclude diffractive features (e.g., optical elements with a GRINprofile, echelletes, etc.) to increase depth of focus. As anotherexample, in some embodiments, a refractive power and/or base curvatureprofile(s) of an intraocular lens surface(s) may contain additionalaspheric terms or an additional conic constant, which may generate adeliberate amount of spherical aberration, rather than correct forspherical aberration. In this manner, light from an object that passesthrough the cornea and the lens may have a non-zero sphericalaberration. Because spherical aberration and defocus are relatedaberrations, having fourth-order and second-order dependence on radialpupil coordinate, respectively, introduction of one may be used toaffect the other. Such aspheric surface may be used to allow theseparation between diffraction orders to be modified as compared to whenonly spherical refractive surfaces and/or spherical diffractive basecurvatures are used. An additional number of techniques that increasethe depth of focus are described in detail in U.S. patent application.Ser. No. 12/971,506, titled “SINGLE MICROSTRUCTURE LENS, SYSTEMS ANDMETHODS,” filed on Dec. 17, 2010, and incorporated by reference in itsentirety herein. In some embodiments, a refractive lens may include oneor more surfaces having a pattern of surface deviations that aresuperimposed on a base curvature (either spherical or aspheric).Examples of such lenses, which may be adapted to provide lensesaccording to embodiments of the present invention, are disclosed in U.S.Pat. No. 6,126,286, U.S. Pat. No. 6,923,539 and U.S. Patent ApplicationNo. 2006/0116763, all of which are herein incorporated by reference intheir entirety.

As discussed above, the piggyback lens that provides increased imagequality at a location on the peripheral retina can be implanted after anIOL configured to provide good foveal vision is implanted. However, forsome patients, the piggyback lens can be implanted at the same time asan IOL configured to provide good foveal vision is being implanted. Forexample, during an ophthalmic surgical procedure, an IOL configured toprovide good foveal vision can be implanted first and the peripheralerror resulting from the IOL can be measured using a diagnosticinstrument. An appropriate piggyback lens that reduces the peripheralerror can be selected and implanted during the same surgical procedure.Various implementations of standard IOLs that are configured to providefoveal correction can be designed to be expandable so that implantationof piggyback lenses when required becomes easy and convenient. Asdiscussed above, piggyback lenses can be used to provide lower orderand/or higher order corrections. In some implementations, one or bothsurfaces of a piggyback lens configured to provide lower orderaberrations correction can be a toric.

Piggyback lenses can also be used for patients with unacceptablerefractive outcomes. This is an attractive solution if the source of theunacceptable refractive outcome is suspected to be an uncertainty ineffective lens position. Replacing the existing IOL would introduce newuncertainties as to where the new lens would be, whereas if it isdetermined that the existing IOL introduces an error of 1.5 Diopter, forexample, a piggyback with 1.5 Diopter correction can be applied toincrease image quality.

Example IOL Design System

FIG. 8 illustrates a block diagram of an example IOL design system 27000for determining properties of an intraocular lens configured to improvevision at a peripheral retinal location. The IOL design system 27000includes a controller 27050 and a computer readable memory 27100 coupledto the controller 27050. The computer readable memory 27100 can includestored sequences of instructions which, when executed by the controller27050, cause the IOL design system 27000 to perform certain functions orexecute certain modules. For example, a PRL location module 27150 can beexecuted that is configured to determine a location of one or more PRLsfor a particular patient. As another example, a deflection module 27200can be executed that is configured to determine a deflected optical axiswhich intersects the determined PRL location at the retina. As anotherexample, an IOL modification module 27250 can be executed that isconfigured to determine properties of the IOL which would deflect atleast a portion of incident light along the determined deflected opticalaxis to the determined PRL. As another example, an IOL selection module27270 can be executed that is configured to select an appropriate orcandidate IOL provided one or more selection parameters including, forexample and without limitation, PRL location and a patient's biometricdata.

The PRL location module 27150 can be configured to determine one or morecandidate PRL locations using analytical systems and methods designed toassess retinal sensitivity and/or retinal areas for fixation. Forexample, the PRL location module 27150 can provide or interface with asystem configured to provide a patient with stimuli and to image thepatient's retina to assess topographic retinal sensitivity and locationsof preferred retinal loci. An example of such a system is amicroperimeter which can be used to determine a patient's PRL bypresenting a dynamic stimulus on a screen and imaging the retina with aninfrared camera. Another example of such a system, a laserophthalmoscope can be used to assess a retinal area used for fixation(e.g., using an infrared eye tracker) which can be used to determinediscrete retinal areas for fixation for various positions of gaze.

The PRL location module 27150 can be configured to bypass the optics ofthe patient. In some instances, optical errors induced by a patient'soptics can cause the patient to select a non-optimal PRL or a PRL whichdoes not exhibit benefits of another PRL, e.g., where a patient selectsan optically superior but neurally inferior region for the PRL.Accordingly, the PRL location module 27150 can advantageously allow theidentification of a PRL which, after application of corrective optics(e.g. the IOLs described herein), would provide superior performancecompared to a PRL selected utilizing a method which includes using thepatient's optics. This may arise where the corrective optics reduce oreliminate the optical errors which are at least a partial cause for apatient selecting a sub-optimal PRL.

The PRL location module 27150 can be configured to determine multiplecandidate locations for the PRL. The preferred or optimal PRL can bebased at least upon several factors including, for example and withoutlimitation, a patient's ability to fixate a point target, distinguishdetail, and/or read; aberrations arising from redirecting images to thecandidate PRL; proximity to the damaged portion of the retina; retinalsensitivity at the candidate location; and the like. The preferred oroptimal PRL can depend on the visual task being performed. For example,a patient can have a first PRL for reading, a second PRL whennavigating, and a third PRL when talking and doing facial recognition,etc. Accordingly, multiple PRLs may be appropriate and an IOL can beconfigured to redirect incident light to the appropriate PRLs usingmultiple zones and/or multiple redirection elements, as describedherein. For example, an IOL can be provided with two or more zones, withone or more zones redirecting light to a designated PRL, where the zonecan be configured to have additional optical power or no additionaloptical power.

The deflection module 27200 can be configured to assess the propertiesof the eye and to determine a deflected optical axis which intersectsthe patient's retina at a PRL. The deflection module 27200 can beconfigured to account for the removal of the natural lens, the opticalproperties of the cornea, the shape of the retina, the location of thePRL, axial distance from the cornea to the PRL and the like to determinethe angle of deflection from the eye's natural optical axis (e.g., theoptical axis of the natural lens, the optical axis of the eye without anIOL, etc.). In some embodiments, the deflection module 27200 can beconfigured to determine aberrations arising from deflecting incidentlight along the deflected optical axis. The aberrations can includeastigmatism, coma, field curvature, etc. The determined aberrations canbe used in the process of refining or tailoring the design of the IOL,where the IOL is configured to at least partially correct or reduce thedetermined aberrations.

The IOL modification module 27250 can be configured to determineadjustments, modifications, or additions to the IOL to deflect lightalong the deflected optical axis and focus images on the PRL. Examplesof adjustments, modifications, or additions to the IOL include, withoutlimitation, the optical systems and methods described herein. Forexample, the IOL can be modified through the introduction of a physicaland/or optical discontinuity to deflect and focus light onto the PRL. Asanother example, one or more redirection elements can be added to one ormore surfaces of the IOL to redirect at least a portion of the lightincident on the eye to the PRL. The redirection elements can include,for example and without limitation, a simple prism, a Fresnel prism, aredirection element with a tailored slope profile, redirection elementwith a tailored slope profile tuned to reduce optical aberrations, adiffraction grating, a diffraction grating with an achromatic coating, adecentered GRIN lens, etc. In some embodiments, multiple redirectionelements and/or multiple modifications can be made to the IOL, asdetermined by the IOL modification module 27250, such that thecombination of modifications and/or additions to the IOL can beconfigured to redirect incident light to different PRLs, to directincident light to different portions of the retina, to provide anoptical power which magnifies an image at the retina, or any combinationof these functions.

The IOL selection module 27270 can be configured to select the IOLdesign, power, deflection, orientation, and the like that would provideacceptable or optimal results for a particular patient. The IOLselection can be based at least in part on the patient's biometricinputs. The IOL selection can incorporate multiple considerations. Forexample, typical IOL power calculation procedures can be used to selectthe spherical IOL power which can be modified to consider the axialdistance from the cornea to the PRL. As another example, customized oradditional constants can be developed for AMD patients which providebetter results for the patients. The deflection and orientation of theIOL during implantation would be given by the PRL location.

The IOL selection can be based at least in part on ray tracing which canenable a computational eye model of the patient to be generated wherethe inputs can be the patient's own biometric data. The optical qualitycan be evaluated considering different IOL deigns and powers, beingselected that which optimizes the optical quality of the patient. Theoptical quality can be evaluated at the PRL or at the PRL and on-axis,for example.

In some embodiments, the IOL selection module 27270 can also comprise arefractive planner which shows patients the expected outcome withdifferent IOL designs and options. This can enable the patient to aid inthe decision as to the appropriate IOL design and to come to a quick andsatisfactory solution.

The IOL design system 27000 can include a communication bus 27300configured to allow the various components and modules of the IOL designsystem 27000 to communicate with one another and exchange information.In some embodiments, the communication bus 27300 can include wired andwireless communication within a computing system or across computingsystems, as in a distributed computing environment. In some embodiments,the communication bus 27300 can at least partially use the Internet tocommunicate with the various modules, such as where a module (e.g., anyone of modules 27150, 27200, or 27250) incorporated into an externalcomputing device and the IOL design system 27000 are communicablycoupled to one another through the communication bus 27300 whichincludes a local area network or the Internet.

The IOL design system 27000 may be a tablet, a general purpose desktopor laptop computer or may comprise hardware specifically configured forperforming the programmed calculations. In some embodiments, the IOLdesign system 27000 is configured to be electronically coupled toanother device such as a phacoemulsification console or one or moreinstruments for obtaining measurements of an eye or a plurality of eyes.In certain embodiments, the IOL design system 27000 is a handheld devicethat may be adapted to be electronically coupled to one of the devicesjust listed. In some embodiments, the IOL design system 27000 is, or ispart of, a refractive planner configured to provide one or more suitableintraocular lenses for implantation based on physical, structural,and/or geometric characteristics of an eye, and based on othercharacteristics of a patient or patient history, such as the age of apatient, medical history, history of ocular procedures, lifepreferences, and the like.

Generally, the instructions stored on the IOL design system 27000 willinclude elements of the methods 2900, and/or parameters and routines forsolving the analytical equations discussed herein as well as iterativelyrefining optical properties of redirection elements.

In certain embodiments, the IOL design system 27000 includes or is apart of a phacoemulsification system, laser treatment system, opticaldiagnostic instrument (e.g, autorefractor, aberrometer, and/or cornealtopographer, or the like). For example, the computer readable memory27100 may additionally contain instructions for controlling thehandpiece of a phacoemulsification system or similar surgical system.Additionally or alternatively, the computer readable memory 27100 maycontain instructions for controlling or exchanging data with one or moreof an autorefractor, aberrometer, tomographer, microperimeter, laserophthalmoscope, topographer, or the like.

In some embodiments, the IOL design system 27000 includes or is part ofa refractive planner. The refractive planner may be a system fordetermining one or more treatment options for a subject based on suchparameters as patient age, family history, vision preferences (e.g.,near, intermediate, distant vision), activity type/level, past surgicalprocedures.

Additionally, the solution can be combined with a diagnostics systemthat identifies the best potential PRL after correction of opticalerrors. Normally, optical errors can restrict the patient from employingthe best PRL, making them prefer neurally worse but optically betterregion. Since this solution would correct the optical errors, it isimportant to find the best PRL of the patient with a method that is notdegraded by optical errors (e.g. adaptive optics). Finally, the solutioncan be utilized to take advantage of the symmetries that exists withregards to peripheral optical errors in many patients.

Prior to replacing a natural crystalline lens with an IOL, an opticalpower of the IOL is typically determined. Generally, the on-axis axiallength, corneal power of the eye, and/or additional parameters can beused to determine the optical power of the IOL to achieve a targetedrefraction with a goal of providing good or optimal optical quality forcentral/foveal vision. However, where there is a loss of central visionan IOL configured to provide good or optimal optical quality for centralvision may result in relatively high peripheral refraction and reducedor unacceptable optical quality at a peripheral location on the retina.Accordingly, systems and methods provided herein can be used to tailorthe optical power of an IOL to provide good or optimal optical qualityat a targeted peripheral location such as a patient's PRL. Theimprovement in optical quality at the peripheral retinal location mayreduce the optical quality at the fovea, but this may be acceptablewhere the patient is suffering from a loss in central vision.

FIG. 9 illustrates parameters used to determine an optical power of anIOL based at least in part at a peripheral retinal location in an eye2800. The eye 2800 is illustrated with a PRL location at 20 degrees withrespect to the optical axis OA. This can represent an intendedpost-operative PRL location, where the PRL location is determined asdescribed elsewhere herein. The on-axis axial length (e.g., axial lengthalong optical axis OA) and PRL-axis axial length (e.g., axial lengthalong a deflected optical axis intersecting the retina at the PRL) canbe measured for the eye 2800 having the indicated PRL location. In somepatients, the axial length in the direction of the PRL can be estimatedfrom the measured on-axis axial length and population averages of ocularcharacteristics measured using a diagnostic instrument. The ocularcharacteristics measured using the diagnostic instrument can includepre-operative refraction, corneal power or other parameters. The cornealtopography can also be measured (e.g., measurements of the anterior andposterior surfaces of the cornea, thickness of the cornea, etc.) andthese measurements can be used, at least in part, to determine thecorneal power.

FIGS. 10A and 10B illustrate implementations of a method 2900 fordetermining an optical power of an IOL tailored to improve peripheralvision. For reference, FIG. 9 provides an illustration of an eye 2800for which the method 2900 can be applied. In addition, FIG. 8 provides ablock diagram of the IOL design system 27000 which can perform one ormore operations of the method 2900. The method 2900 can be used todetermine the optical power of the IOL which improves or optimizesoptical quality at a PRL location. However, the method 2900 can be usedto determine the optical power of an IOL to be used in any suitableprocedure, such as where there is a loss of central vision, where thePRL is outside the fovea, where the PRL is within the fovea, where thereare multiple PRLs, where the PRL is at a relatively large or smalleccentricity, or the like.

With reference to FIGS. 10A and 10B, in block 2905, the on-axis axiallength is measured. The on-axis axial length can be measured, forexample, from the anterior surface of the cornea to the retina. Thelength can be determined using any number of standard techniques formaking measurements of the eye. In some embodiments, instead ofmeasuring the on-axis axial length, it is estimated based on computermodels of eyes, statistical data (e.g., average on-axis distance foreyes with similar characteristics), or a combination of these. In someembodiments, the on-axis axial length is determined using a combinationof measurement techniques and estimation techniques.

With reference to FIG. 10A, in block 2910, the PRL-axis axial length ismeasured. The PRL-axis axial length can be taken as the length along adeflected optical axis to the PRL location at the retina. The length canbe measured from the anterior surface of the cornea, from the point ofdeflection from the optical axis, or any other suitable location. Insome embodiments, the PRL-axis axial length can be estimated based on acombination of the eccentricity of the PRL, the PRL location, theretinal shape, the on-axis axial length, the distance from a proposedIOL location to the PRL, or any combination of these. In someembodiments, instead of measuring the PRL-axis axial length, it isestimated based on computer models of eyes, statistical data (e.g.,average PRL-axis axial length for eyes with similar PRL locations andcharacteristics), or a combination of these. In some embodiments, thePRL-axis axial length is determined using a combination of measurementtechniques and estimation techniques. In some embodiments, the PRL-axisaxial length can be estimated based on population averages of ocularcharacteristics measured using a diagnostic instrument, as shown inblock 2907 and 2912 of FIG. 10B. The measured ocular characteristics caninclude on-axis axial length, pre-operative refraction power, cornealpower or other measured parameters.

In block 2915, the corneal shape is determined. The anterior and/orposterior surfaces of the cornea can be determined using measurements,estimations, simulations, or any combination of these. The corneal powercan be derived or determined based at least in part on the cornealshape, that can be measured with tomography or topographic techniques.In some embodiments, the corneal power is determined based onmeasurements of optical properties of the cornea.

In block 2920, the position of the IOL is estimated. The position of theIOL can be estimated based at least in part on an estimation of alocation which would provide good optical quality at the fovea. Thelocation can be one that takes into account the corneal power ortopography and the on-axis axial length. Some other inputs that can betaken into consideration to predict the postoperative IOL position arethe axial position of the crystalline lens from the anterior cornea,which is defined as anterior chamber depth, crystalline lens thickness,vitreous length on axis combinations of thereof. In some embodiments,the estimated position of the IOL can be refined by taking into accountthe PRL-axis axial length and/or eccentricity of the PRL. In someembodiments, the estimated IOL location can take into account data fromprevious procedures, with or without including the same IOL design. Forexample, historic data from cataract surgeries can be used as that datamay indicate a good estimate of the IOL position.

In some embodiments, rather than determining an estimated initialposition of the IOL configured to provide good optical quality forcentral/foveal vision, the estimated position can be configured toprovide good optical quality for peripheral vision. Similar proceduresas described for determining the IOL position that provides with goodoptical quality on axis can be applied in this case. Therefore, thelocation of the IOL can be predicted from biometric measurements,including corneal shape or power, axial length, either on axis or to thePRL, anterior chamber depth, crystalline lens thickens and/or vitreouslength, either defined on axis or to the PRL. Retrospective data fromprevious cataract procedures aimed to restore vision on axis or at thePRL can also been taken into consideration to optimize the prediction ofthe IOL position that provide with good optical quality at the PRL. Inaddition to that, the estimated position can be based at least in parton procedures, for example, where the patient was suffering from centralvision loss (e.g., due to AMD). Similarly, data can be used where thepositions of IOLs have been tabulated and recorded as a function of theproperties of the IOLs (e.g., sphere power, cylinder power, cylinderaxis, redirection angle, etc.) and such properties were tailored usingthe systems and methods described herein. Data from such procedures canbe subjected to further selection criteria based on the location of thePRLs of the patients, where the locations were, for example and withoutlimitation, outside a determined angular range of the fovea, at aneccentric angle greater and/or less than a threshold eccentricity, at aneccentricity within a provided range of the PRL of the patient, or anycombination of these. The data can be selected based on these criteriaor other similar criteria which may improve the estimated IOL positionfor patients suffering from a loss of central vision.

In block 2925, the sphere and cylinder power of the IOL is determinedusing an IOL power calculation. The IOL power calculation can beconfigured to provide a spherical power for the IOL, a cylinder powerfor the IOL, and/or the cylinder axis, wherein the combination of one ormore of these parameters is configured to provide good or optimaloptical quality at the PRL location when the IOL is implanted at theestimated location.

The IOL power calculation can use as input data, for example and withoutlimitation, on-axis axial length (e.g., the measurement or valueprovided in block 2905), corneal power (e.g., the value determined frommeasurements acquired in block 2915), fixation angle(s) (e.g.,horizontal and vertical angles of fixation), intended post-operativerefraction, eccentricity of the PRL, eccentric axial length (e.g., fromthe anterior cornea to the location of the PRL on the retina, such asthe measurement or value provided in block 2910), predicted futuremovement of the PRL (e.g., due to progression of a disease such as AMD),a partial or full map of the retinal shape, a partial or full map of theretinal health, corneal topography, or the like. In some embodiments,the IOL power calculation is a regression formula, a theoretical formula(e.g., based on paraxial optical equations, ray tracing, etc.), or acombination of both of these. In some embodiments, current IOL powercalculation procedures can be used while considering the eccentric axiallength together with the corneal power. In those cases, A constants foreither lenses to restore vision on axis after cataract surgery can beused. In certain embodiments, specific A constants can be determineddepending on the design and/or eccentricity.

In some embodiments, ray tracing can be used to determine properties ofthe IOL which improve or reduce peripheral errors at the PRL based atleast in part on the estimated IOL position. The ray tracing canincorporate relevant measurements and data including, for example andwithout limitation, the measurements of the eye (e.g., the measurementsor values determined in blocks 2905, 2910, and 2915), the position ofthe PRL, the estimated position of the IOL (e.g., as provided in block2920), and the like. This information can be used as input in a computerexecutable module or program stored in non-transitory computer memory,the module or program configured to cause a computer processor toexecute instructions configured to perform ray tracing which can beaccomplished, for example, by the IOL design system 27000 describedherein with reference to FIG. 8. The ray tracing system can be used tofind the sphere power, cylinder power, and/or cylinder axis of the IOLto be implanted in the eye 2800, wherein these parameters are tailoredto improve or optimize for peripheral aberrations at the PRL location.Any standard ray tracing system or scheme can be used to accomplish thegoal of tailoring the sphere power, cylinder power, and/or cylinderaxis.

In some embodiments, the output of the IOL power calculation can be usedfor selecting an appropriate or suitable IOL where the output of the IOLpower calculation includes, for example and without limitation, dioptricpower, cylinder power, cylinder axis, deflection angle, and the like.These output values can be used in the selection of the IOL wherein theselected IOL has one or more properties within an acceptable range ofthe output values. In some embodiments, the IOL power calculation can beused to define or select IOL design parameters that improve or optimizeoptical quality as a function of retinal location(s) or retinal area(s).

In some embodiments, the IOL power calculation can be similar orequivalent to a power calculation configured to provide good or optimalon-axis optical quality (e.g., for central/foveal vision) where theaxial length used is the PRL-axis axial length rather than the on-axisaxial length. In some embodiments, the PRL-axis axial length can bedetermined based at least in part on the eccentricity of the PRL, thePRL location, the retinal shape, the length from the IOL to the PRL, orany combination of these. These and other input values can be determinedbased on measurements of a particular patient (e.g., the patient toreceive the IOL), a group of patients, from computer models orsimulations, or a combination of these sources. In an alternativeembodiment, both, the axial length on axis and to the PRL can beconsidered, so that the IOL selected is that which maximizes the opticalquality at the PRL and at, to some extended, at the fovea. In anotherembodiment, the axial length to several PRL can be considered, so thatthe IOL selected is that which has the characteristics that optimize theoptical quality at each PRL.

In some embodiments, the IOL power calculation can be used formultifocal IOLs for patients suffering from a loss of central vision.The IOL power calculation can be configured to provide valid andacceptable results where the PRL lies within the fovea. In analternative embodiment the add power of the multifocal IOL can beselected as that which maximizes the optical quality either at the PRLand/or the fovea.

In some embodiments, the IOL power calculation can be used inconjunction with the other systems and methods described hereinconfigured to redirect and focus images to the PRL. The powercalculations can be used to tailor the properties of the IOL, the IOLbeing used in combination with one or more redirection elements toreduce peripheral aberrations and/or improve peripheral image qualityfor patients suffering from a loss of central vision.

Additional Embodiments for Selecting IOL Sphere and Cylinder

As detailed above, IOL power is typically selected based primarily onaxial length and corneal power, and any toric parts mostly depend on thetoricity of the cornea. However, any spherical surface for which thelight is obliquely incident will exhibit a large degree of astigmatism.The embodiments below detail additional ways to properly select sphereand cylinder of the IOL for the AMD patient.

In one embodiment, sphere selection is based on population data. Here,no new biometry readings are needed. Instead, the patients areclassified depending on foveal refraction, from which the averageperipheral spherical profile for that refractive group is selected. Fromthe profile, spherical refraction at the PRL can be determined.

As seen above, sphere selection may also be based on individual data.The peripheral sphere can be determined through an axial lengthmeasurement to the PRL. This requires the modification of current axiallength methods, since the oblique incidence on the crystalline lens willmean a longer than average passage through the lens, which has a higherindex of refraction, increasing the difference between the optical pathlength and the physical length. The increased contribution can bepredicted based on PRL location.

In one embodiment, astigmatism determination is based on populationdata. The inter-subject variation in astigmatism for a given angle isrelatively modest. Therefore, the contribution of the oblique incidenceat any given eccentricity can be predicted based on PRL location. Forthese calculations, PRL location should be determined based on theoptical axis, which is on average between about 1-10 degreeshorizontally and between about 1-5 degrees vertically from the fovea.The axis of the astigmatism can also be determined from the location,e.g. for a horizontal PRL the axis is 180 and for a vertical PRL theaxis is 90, for a negative cylinder convention. Additionally, theastigmatism contribution of the IOL selected can be incorporated, in aniterative selection procedure. To this astigmatism, the cornealastigmatism from the cornea can also be added.

In another embodiment, astigmatism determination is based on individualdata. Even for persons that are foveally emmetropic, the obliqueastigmatism at e.g. 20 degrees can vary between 0.75 D and 2 D. Thereare several possible reasons for this: 1) The individual differences inangle between fovea and optical axis; 2) Individual differences incorneal power means the oblique astigmatism has different values; 3)Pupil position relative lens and cornea can be different leading tovariation in the IOL position for different individuals. Biometryreading for any or all of these parameters can then be incorporated intoan individual eye model, to select the best IOL cylinder power for thepatient.

CONCLUSION

The above presents a description of systems and methods contemplated forcarrying out the concepts disclosed herein, and of the manner andprocess of making and using it, in such full, clear, concise, and exactterms as to enable any person skilled in the art to which it pertains tomake and use this invention. The systems and methods disclosed herein,however, are susceptible to modifications and alternate constructionsfrom that discussed above which are within the scope of the presentdisclosure. Consequently, it is not the intention to limit thisdisclosure to the particular embodiments disclosed. On the contrary, theintention is to cover modifications and alternate constructions comingwithin the spirit and scope of the disclosure as generally expressed bythe following claims, which particularly point out and distinctly claimthe subject matter of embodiments disclosed herein.

Although embodiments have been described and pictured in an exemplaryform with a certain degree of particularity, it should be understoodthat the present disclosure has been made by way of example, and thatnumerous changes in the details of construction and combination andarrangement of parts and steps may be made without departing from thespirit and scope of the disclosure as set forth in the claimshereinafter.

As used herein, the term “controller” or “processor” refers broadly toany suitable device, logical block, module, circuit, or combination ofelements for executing instructions. For example, the controller 27050can include any conventional general purpose single- or multi-chipmicroprocessor such as a Pentium® processor, a MIPS® processor, a PowerPC® processor, AMD® processor, ARM processor, or an ALPHA® processor. Inaddition, the controller 27050 can include any conventional specialpurpose microprocessor such as a digital signal processor. The variousillustrative logical blocks, modules, and circuits described inconnection with the embodiments disclosed herein can be implemented orperformed with a general purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array (FPGA), or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.Controller 27050 can be implemented as a combination of computingdevices, e.g., a combination of a DSP and a microprocessor, a pluralityof microprocessors, one or more microprocessors in conjunction with aDSP core, or any other such configuration.

Computer readable memory 27100 can refer to electronic circuitry thatallows information, typically computer or digital data, to be stored andretrieved. Computer readable memory 27100 can refer to external devicesor systems, for example, disk drives or solid state drives. Computerreadable memory 27100 can also refer to fast semiconductor storage(chips), for example, Random Access Memory (RAM) or various forms ofRead Only Memory (ROM), which are directly connected to thecommunication bus or the controller 27050. Other types of memory includebubble memory and core memory. Computer readable memory 27100 can bephysical hardware configured to store information in a non-transitorymedium.

Methods and processes described herein may be embodied in, and partiallyor fully automated via, software code modules executed by one or moregeneral and/or special purpose computers. The word “module” can refer tologic embodied in hardware and/or firmware, or to a collection ofsoftware instructions, possibly having entry and exit points, written ina programming language, such as, for example, C or C++. A softwaremodule may be compiled and linked into an executable program, installedin a dynamically linked library, or may be written in an interpretedprogramming language such as, for example, BASIC, Perl, or Python. Itwill be appreciated that software modules may be callable from othermodules or from themselves, and/or may be invoked in response todetected events or interrupts. Software instructions may be embedded infirmware, such as an erasable programmable read-only memory (EPROM). Itwill be further appreciated that hardware modules may comprise connectedlogic units, such as gates and flip-flops, and/or may comprisedprogrammable units, such as programmable gate arrays, applicationspecific integrated circuits, and/or processors. The modules describedherein can be implemented as software modules, but also may berepresented in hardware and/or firmware. Moreover, although in someembodiments a module may be separately compiled, in other embodiments amodule may represent a subset of instructions of a separately compiledprogram, and may not have an interface available to other logicalprogram units.

In certain embodiments, code modules may be implemented and/or stored inany type of computer-readable medium or other computer storage device.In some systems, data (and/or metadata) input to the system, datagenerated by the system, and/or data used by the system can be stored inany type of computer data repository, such as a relational databaseand/or flat file system. Any of the systems, methods, and processesdescribed herein may include an interface configured to permitinteraction with users, operators, other systems, components, programs,and so forth.

What is claimed is:
 1. An ophthalmic lens configured to improve visionfor a patient's eye, the lens comprising: an optic with a first surfaceand a second surface opposite the first surface, wherein the optictogether with a cornea and an existing lens in the patient's eye isconfigured to improve image quality of an image produced by lightincident on the patient's eye at an oblique angle with respect to theoptical axis and focused at a peripheral retinal location disposed at adistance from the fovea, and wherein the image quality is improved byreducing oblique astigmatism at the peripheral retinal location.
 2. Thelens of claim 1, wherein the image quality is improved by reducing comaat the peripheral retinal location.
 3. The lens of claim 1, wherein theoblique angle is between about 1 degree and about 25 degrees.
 4. Thelens of claim 1, wherein at least one of the first or the second surfaceis a toric surface, an aspheric, a higher order aspheric surface, anaspheric Zernike surface or a Biconic Zernike surface.
 5. The lens ofclaim 1, wherein a thickness of the optic varies about a periphery ofthe optic.
 6. The intraocular lens of claim 1, wherein the image has amodulation transfer function (MTF) of at least 0.3 for a spatialfrequency of 30 cycles/mm for both the tangential and the sagittal fociat the peripheral retinal location.
 7. The intraocular lens of claim 1,wherein the image has a modulation transfer function (MTF) of at least0.5 for a spatial frequency of 100 cycles/mm for both the tangential andthe sagittal foci at the fovea.
 8. The lens of claim 1, wherein theoptic includes an optical axis that intersects the first and the secondsurface and a thickness of the optic along the optical axis is betweenabout 0.1 mm and about 0.9 mm.
 9. The lens of claim 8, wherein the opticis symmetric about the optical axis of the optic.
 10. The lens of claim8, wherein the optic is asymmetric about the optical axis of the optic.11. The lens of claim 1, wherein the optic is configured to be implantedbetween the iris and the existing lens.
 12. The lens of claim 1, whereinthe existing lens is configured to provide foveal vision.
 13. The lensof claim 1, wherein the first and the second surface are convex.
 14. Thelens of claim 1, wherein the first surface is concave and the secondsurface is convex.
 15. The lens of claim 1, wherein the first surfaceand the second surface are concave.
 16. The intraocular lens of claim 1,wherein the optic includes diffractive features.
 17. The intraocularlens of claim 1, wherein the optic element includes prismatic features.18. A method of selecting an intraocular lens (IOL) configured to beimplanted in a patient's eye, the method comprising: obtaining at leastone characteristic of the patient's eye using a diagnostic instrument;and selecting an IOL having an optical power that reduces optical errorsin an image produced at a peripheral retinal location of the patient'seye disposed at a distance from the fovea, wherein the image is producedby focusing light incident on the patient's eye at an oblique angle withrespect to an optical axis intersecting the patient's eye at theperipheral retinal location by a combination of the optic, an existinglens and the patient's cornea, and wherein the optical power of the IOLis based on the obtained characteristic.
 19. The method of claim 18,wherein the obtained characteristic includes axial length along theoptical axis of the patient's eye and corneal power.
 20. The method ofclaim 19, wherein the optical power is obtained from an estimate of anaxial length along an axis which deviates from the optical axis andintersects the retina at the peripheral retinal location, the estimatebased on the axial length along the optical axis of the patient's eyeand corneal power.
 21. The method of claim 18, wherein the obtainedcharacteristic is selected from the group consisting of axial lengthalong the optical axis of the patient's eye, corneal power based atleast in part on measurements of topography of the cornea, an axiallength along an axis which deviates from the optical axis and intersectsthe retina at the peripheral retinal location, a shape of the retina,and a measurement of optical errors at the peripheral retinal location.22. The method of claim 18, wherein at least one of the surfaces of theIOL includes a redirecting element.
 23. The method of claim 22, whereinthe redirecting element comprises a diffractive feature.
 24. The methodof claim 22, wherein the redirecting element comprises a prismaticfeature.
 25. The method of claim 18, wherein the image has reduced coma.26. The method of claim 18, wherein the image has reduced astigmatism.27. The method of claim 18, wherein the oblique angle is between about 1degree and about 25 degrees.
 28. The method of claim 18, wherein the IOLis configured such that the image has a modulation transfer function(MTF) of at least 0.3 for a spatial frequency of 30 cycles/mm for bothtangential and sagittal foci.